NGK Spark Plug Dimensions: 8mm, 10mm, 12mm, 18mm & Racing Plugs
NGK Spark Plug Dimensions: 8mm, 10mm, 12mm, 18mm & Racing Plugs
421 plugs. The physical dimensions of each plug in the NGK range: thread size, reach, hex, seat type and whether the tip is projected. This is what decides whether a plug will physically fit and seal, before heat range comes into it. Plug codes are links — click one to go straight to that plug on our shop.
Reach and seat type are not interchangeable. A plug that is too long can hit the piston; one that is too short leaves thread exposed in the combustion chamber and will not transfer heat properly. A tapered-seat plug will not seal in a gasket-seat head. Match all of thread, reach and seat, then match the heat range.
- 12mm Spark Plugs
- 10mm Spark Plugs
- 18mm Spark Plugs
- 8mm Spark Plugs
- Racing Spark Plugs
- PF1/2S Spark Plugs
- Thread size not listed
12mm Spark Plugs 177 plugs
| NGK plug | Range | Reach | Hex | Seat | Notes |
|---|---|---|---|---|---|
| DCPR6EIX · DCPR7EIX · DCPR8EIX · DCPR9EIX · KR8DI | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Loose | Projected |
| DF6H-11A | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Extended Shell Extended Projection Wide Gap Dual Fine Electrode |
| DF8H-11B · DILKR6D11G · DILKR7A11 | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected, Wide Gap Dual Fine Electrode |
| DILKAR6A11 · DILKAR7G11GS · DILKAR7H11GS | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected Wide Gap Dual Fine Electrode |
| DILKAR7B8 · DILKAR8A8 | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected Dual Fine Electrode |
| DILKAR7C9H | Iridium | 28.5mm Reach | 14mm Hex | Gasket, Solid | Projected Dual Fine Electrode |
| DILKR7B6 · DILKR8B6 | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected Dual Fine Electrode |
| DILZKAR7B11 · ILZKR7B11 · ILZKR7B-11S | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Extended Projection Wide Gap |
| DILZKAR7B11G · DILZKAR7C11S · DILZKR7A11G · DILZKR7B11GS · DILZKR711DS | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid, Wide | Extended Projection Extended Shell, DFE Gap |
| DPR7EIX-9 · DPR8EIX-9 · DPR9EIX-9 · IJR7AP | Iridium | 3/4" Reach | 18mm Hex | Gasket, Stud | Projected, Wide Gap |
| DR7EIX · DR8EIX · DR9EIX | Iridium | 3/4" Reach | 18mm Hex | Gasket, Stud | |
| IKR7H8 · KR8AI · KR8BI | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected 2-Ground Electrode |
| ILKAR6C10 · ILKAR7B11 · ILKAR7C10 · ILKAR7L11 · LKAR6AIX-11 · LKAR7BIX-11S · LKAR8AI-9 | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected Wide Gap |
| ILKAR8H6 | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected |
| ILKR7B8 · ILKR7E6 · ILKR8E6 · ILKR8Q7 · ILKR9Q7G · LKR6CIX · LKR7AIX · SILKR8B8DS | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected |
| ILNAR8B7G · SILNAR7B7 · SILZNAR6D9 · SILZNAR8C7H | Iridium | 25mm Reach | 14mm Hex | Projected Tapered Solid | |
| ILZKAR7A10 · ILZKAR7B11 | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Extended Projection Wide Gap |
| ILZKAR8H8S · ILZKAR8J8SY · ILZKR7A · ILZKR8A | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Extended Projected Extended Shell |
| ILZKBR7B8DG · SILZKBR8D8S · SILZKBR8E8S | Iridium | 26.5mm Reach | Bi-Hex 14mm | Gasket, Solid | Extended Projection |
| ILZNAR8A7G | Iridium | 25 mm Reach | 14 mm, Hex | Extended Shell | |
| IZKR7B | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | Extended Shell |
| KR9CI | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected |
| LKAR8BI9 · LKAR9BI9 · LKAR9BI-10 | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Stud | Projected Wide Gap |
| LKR7BGP-S · LKR7DIX-11S | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected Wide Gap |
| LZKR6AIX · SILKR8A-S · SILZKR6B10E · SILZKR6B11 · SILZKR7B8E · SILZKR7B11 · SILZKR7E8EG · SILZKR7E9G · SILZKR7E11 | Iridium | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Extended Projection |
| SILZKAR7B11 | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Extended Projection PSPE, Wide Gap |
| SILZKAR7E8S | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Extended Shell Projected |
| SILZKFR8D7S · SILZKFR8E7S | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Solid | Extended Shell Extended Projected |
| SILZKGR8B8S · SILZKGR8C8S | Iridium | 26.5mm Reach | Bi-Hex 14mm | Gasket, Special | Extended Projection Terminal |
| SIZKBR8A8HS | Iridium | 23.7 mm Reach | Bi-Hex, 14 mm | Gasket, Solid | Extended Shell Extended Projection SPE |
| ZNAR6AIX-11 · ZNAR7AIX | Iridium | 26.5mm Reach | 14mm Hex | Tapered, Solid | Extended Projection Wide Gap |
| R2349-10 · R2349-11 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Surface Discharge Resistor |
| R2525-9 · R2525-10 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Loose | Platinum Resistor |
| R2556B-8 · R2556B-9 · R2556B-10 · R2556G-8 · R2556G-9 · R2556G-10 · R2558E-9 | NGK Racing | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Iridium Resistor |
| DCPR7EGP · DCPR8EKP · PKR7A | Platinum | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected 2-Ground Electrode |
| LKAR6AGP · LKAR7AGP-D · LKAR7BGP-S · LKR6BGP-E | Platinum | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected Wide Gap |
| LKR7BGP-8 · PLKR6A · PLKR7A · PLKR7B8E | Platinum | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected |
| LKR8AP | Platinum | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected 2-Ground Electrode |
| LZKR6AGP-E | Platinum | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Extended Projection |
| PJR7A | Platinum | 3/4" Reach | 18mm Hex | Gasket, Stud | Projected |
| PLZKAR6A-11 | Platinum | 26.5mm Reach | 14mm Hex | Gasket, Solid | Extended Projection Wide Gap |
| PLZKBR7B8DG | Platinum | 26.5mm Reach | Bi-Hex 14mm | Gasket, Solid | Extended Projection |
| PZNAR6A11H · ZNAR6AGP | Platinum | 26.5mm Reach | 14mm Hex | Tapered, Solid | Extended Projection Wide Gap |
| LKAR6AHX · LKAR7AHX-S | Ruthenium HX | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected, Wide Gap Dual Fine Electrode |
| LKAR8BHX | Ruthenium HX | 26.mm Reach | 14mm Hex | Gasket, Solid | Projected PSPE |
| LKR6AHX · LKR7AHX-S | Ruthenium HX | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected, Wide Gap Dual Fine Electrode |
| LKR6BHX-E · LKR7BHX · LKR8BHX-S | Ruthenium HX | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected PSPE |
| D6EA · D7EA · D8EA · D9EA · J9A · J10A | Standard, non-resistor | 3/4" Reach | 18mm Hex | Gasket, Stud | |
| D6HA · D8HA | Standard, non-resistor | 1/2" Reach | 18mm Hex | Gasket, Stud | |
| DP6EA-9 · DP7EA-9 · DP8EA-9 · DP9EA-9 | Standard, non-resistor | 3/4" Reach | 18mm Hex | Gasket, Stud | Projected, Wide Gap |
| DCPR6E · DCPR8EKC · DCPR9E · KR9C-G | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected 2-Ground Electrode |
| DCPR7E · DCPR8E | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Loose | Projected |
| DCPR7E-N-10 | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected, Wide Gap |
| DPR5EA-9 · DPR6EA-9 · DPR7EA-9 · DPR8EA-9 · DPR9EA-9 | Standard, resistor | 3/4" Reach | 18mm Hex | Gasket, Stud | Projected, Wide Gap |
| DPR6EB-9 | Standard, resistor | 3/4" Reach | 18mm Hex | Gasket, Solid | Projected, Wide Gap |
| DPR8Z · DPR9Z | Standard, resistor | 3/4" Reach | 18mm Hex | Gasket, Stud | Projected, Extended Shell |
| DR4HS · DR5HS · DR6HS · DR8HS | Standard, resistor | 1/2" Reach | 18mm Hex | Gasket, Stud | |
| DR7EA · DR7ES · DR8EA · DR8ES · DR9EA · JR9B · JR10B | Standard, resistor | 3/4" Reach | 18mm Hex | Gasket, Stud | |
| DR7EB · DR8EB | Standard, resistor | 3/4" Reach | 18mm Hex | Gasket, Solid | |
| DR8ES-L | Standard, resistor | 3/4" Reach | 18mm Hex | Gasket, Stud | Half Heat Range Cooler |
| JR8C · JR9C | Standard, resistor | 3/4" Reach | 18mm Hex | Gasket, Stud | 2-Ground Electrode |
| KR9E-G | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected |
| LKAR8A-9 | Standard, resistor | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected Wide Gap |
| LKR6E · LKR7B-9 · LKR7E | Standard, resistor | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected |
| LKR8A | Standard, resistor | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected 2-Ground Electrode |
| LZKAR7A | Standard, resistor | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Extended Projection |
10mm Spark Plugs 140 plugs
| NGK plug | Range | Reach | Hex | Seat | Notes |
|---|---|---|---|---|---|
| CPR7EAIX-9 | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Stud | Projected, Wide Gap |
| CR6EIA-9 · CR7EIA-9 · CR8EIA-9 · CR8EIA-10 · CR9EIA-9 | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Stud | Wide Gap |
| CR6HIX · CR7HIX · CR8HIX | Iridium | 1/2" Reach | 5/8" Hex | Gasket, Stud | |
| CR7EIX · CR8EIX · CR9EIX · CR10EIX | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Loose | |
| CR8EHIX-9 · CR9EHI-9 · CR9EHIX-9 · IMR8C-9H · IMR9A-9H · IMR9C-9H · IMR9C-9HE · IMR9C-9HES · IMR9E-9HES | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Stud | Partial Thread, Wide Gap |
| CR8EIB-9 · CR9EIB-9 · MR7BI-8 · MR8AI9 · MR8BI-8 | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | |
| CR8EIB-10 | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | Wide Gap |
| DIMR8B10 · DIMR8C10 | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected, Wide Gap Dual Fine Electrode |
| IMR8E-9HES | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected, Wide Gap |
| IMR9B-9H · IMR9D-9H | Iridium | 3/4" Reach | 5/8" Hex | Gasket, Solid | Partial Thread, Wide Gap |
| LMAR7DI-10 | Iridium | 26.5mm Reach | 14mm Hex | Gasket, Stud | Projected |
| LMAR8AI-8 · LMAR8BI-9 · LMAR9AI-8 | Iridium | 26.5 mm Reach | 14 mm Hex | Gasket, Solid | |
| LMAR9AI-10 | Iridium | 26.5 mm Reach | 14 mm Hex | Gasket, Solid | Wide Gap |
| SILMAR7A9S · SILMAR8A9S · SILMAR9A9S · SILMAR10A9S | Iridium | 26.5mm Reach | 14mm Hex, SPE | Gasket, Solid | |
| SILMAR9B9 | Iridium | 26.5mm Reach | 5/8" Hex, SPE | Gasket, Stud | |
| R0045J-9 · R0045J-11 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Surface Discharge Non-Resistor |
| R0045Q-9 · R0045Q-10 · R0045Q-11 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Loose | Surface Discharge Resistor |
| R0373A-9 · R0373A-10 · R0373A-11 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Stud | Fine Wire, Iridium Resistor |
| R0406A-8 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Fine Wire, Iridium Resistor |
| R0409B-8 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Stud | Fine Wire Resistor, Partial Thread |
| R0451B-8 | NGK Racing | 26.5mm Reach | 14mm Hex | Gasket, Solid | Fine Wire, Iridium Resistor |
| CR8EKPA · CR9EKPA | Platinum | 3/4" Reach | 5/8" Hex | Gasket, Stud | 2-Ground Electrode |
| PMR7A · PMR8A · PMR8B · PMR9A | Platinum | 3/4" Reach | 5/8" Hex | Gasket, Solid | |
| SPMR8A6HDG | Platinum | 22 mm Reach | 5/8" Hex | Gasket, Solid | |
| C2H · C6HSA · C7HSA · C8HA · C8HSA | Standard, non-resistor | 1/2" Reach | 5/8" Hex | Gasket, Stud | |
| C7E · C8E · C9E | Standard, non-resistor | 3/4" Reach | 5/8" Hex | Gasket, Stud | |
| C8EH-9 | Standard, non-resistor | 3/4" Reach | 5/8" Hex | Gasket, Stud | Partial Thread, Wide Gap |
| C-50 | Standard, non-resistor | 8.5mm Reach | 13/16" Hex | Gasket, Loose | |
| CM-6 | Standard, non-resistor | 8.6mm Reach | 5/8" Hex | Gasket, Solid | |
| CMR4A · CMR6A · CMR7A · CMR7A-5 | Standard, resistor | 3/8" Reach | 5/8" Hex | Gasket, Solid | Compact |
| CMR4H · CMR5H · CMR6H · CMR7H · CMR8H | Standard, resistor | 1/2" Reach | 5/8" Hex | Gasket, Solid | Compact |
| CMR7H-10 | Standard, resistor | 1/2" Reach | 5/8 Hex | Gasket, Solid | Compact Wide Gap |
| CPR6EA-9 · CPR6EA-9S · CPR7EA-9 · CPR8EA-9 · CPR9EA-9 | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Stud | Projected, Wide Gap |
| CPR6EB-9 · CPR8EB-9 · CPR9EB-9 | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected, Wide Gap |
| CPR8E · MR7F · MR8F · MR9F | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Solid | Projected |
| CR4HSA · CR5HSA · CR6HS · CR6HSA · CR7HS · CR7HSA · CR8HSA | Standard, resistor | 1/2" Reach | 5/8" Hex | Gasket, Stud | |
| CR4HSB · CR5HSB · CR6HSB · LR4C-E · LR8B | Standard, resistor | 1/2" Reach | 5/8" Hex | Gasket, Solid | |
| CR5EH-9 · CR6EH-9 · CR7EH-9 · CR8EH-9 · CR9EH-9 | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Stud | Partial Thread, Wide Gap |
| CR6E · CR7E · CR8E · CR9E · CR10E | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Stud | |
| CR7EB · CR8EB · CR9EB | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Solid | |
| CR7EK · CR8EK · CR9EK · CR10EK | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Stud | 2-Ground Electrode |
| CR7EKB · CR8EKB · CR9EKB | Standard, resistor | 3/4" Reach | 5/8" Hex | Gasket, Solid | 2-Ground Electrode |
| CR7HSA-9 | Standard, resistor | 1/2" Reach | 5/8" Hex | Gasket, Stud | Wide Gap |
| LMAR6A-9 · LMAR7A-9 · LMAR8A-9 · LMAR8A-9S | Standard, resistor | 26.5mm Reach | 14mm Hex | Gasket, Stud | Projected |
| LMAR6C-9 · LMAR8C-9 | Standard, resistor | 26.5mm Reach | 14mm Hex | Gasket, Solid | Projected |
| LMAR8D-J · LMAR9D-J | Standard, resistor | 26.5mm Reach | 14mm Hex | Gasket, Solid | 2-Ground Electrode |
| LMAR8F-9 | Standard, resistor | 26.5 mm Reach | 14 mm Hex | Gasket, Solid | |
| LMAR9E-J | Standard, resistor | 26.5mm Reach | 14mm Hex | Gasket | Projected 2-Ground Electrode |
| MAR8B-JDS | Standard, resistor | 3/4" Reach | 14 mm Hex | Partial Thread | |
| MAR9A-J · MAR10A-J | Standard, resistor | 3/4" Reach | 14mm Hex | Gasket, Solid | 2-Ground Electrode |
18mm Spark Plugs 12 plugs
| NGK plug | Range | Reach | Hex | Seat | Notes |
|---|---|---|---|---|---|
| WR5IX | Iridium | .460" Reach | 13/16" Hex | Tapered, Solid | Projected |
| R8102A-10 | NGK Racing | 16mm Reach | 25.4mm Hex | Gasket, Loose | Non-Resistor |
| A6FS | Standard, non-resistor | .460" Reach | 13/16" Hex | Tapered, Solid | |
| AB-2 · AB-6 · AB-7 · AB-8 | Standard, non-resistor | 12mm Reach | 13/16" Hex | Gasket, Loose | |
| AP7FS · AP8FS | Standard, non-resistor | .460" Reach | 13/16" Hex | Tapered, Solid | Projected |
| AR6FS | Standard, resistor | .460" Reach | 13/16" Hex | Tapered, Solid | |
| WR4-1 | V-Power | .460" Reach | 13/16" Hex | Tapered, Solid | Extended Projection |
| WR5 | V-Power | .460" Reach | 13/16" Hex | Tapered, Solid | Projected |
8mm Spark Plugs 3 plugs
| NGK plug | Range | Reach | Hex | Seat | Notes |
|---|---|---|---|---|---|
| ER8EHIX · ER9EHIX | Iridium | 3/4" Reach | 13mm Hex | Gasket, Stud | |
| ER9EH | Standard, resistor | 3/4" Reach | 13mm Hex | Gasket, Stud |
Racing Spark Plugs 79 plugs
| NGK plug | Range | Reach | Hex | Seat | Notes |
|---|---|---|---|---|---|
| B8EG · B9EG · B10EG · B11EG | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Loose | Fine Wire Non-Resistor |
| B8EG SOLID · B9EG SOLID | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Solid | Fine Wire Non-Resistor |
| B10EGP · B10EGV · R4118S-8 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Loose | Gold Palladium Non-Resistor |
| BR8EG · BR9EG | NGK Racing | 3/4" Reach | 13/16" Hex | Fine Wire | |
| BR8EG SOLID · BR9EG SOLID · BR9EG-N-8 · BR10EG SOLID | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Solid | Fine Wire Resistor |
| R5184-105 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Loose | Gold Palladium Low Angle Ground Electrode Non-Resistor |
| R5671A-7 · R5671A-8 · R5671A-9 · R5671A-10 · R5671A-11 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | V-Power Non-Resistor |
| R5672A-8 · R5672A-9 · R5672A-10 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | V-Power, Projected Non-Resistor |
| R5673-9 · R5673-10 | NGK Racing | .460" Reach | 5/8" Hex | Tapered, Solid | V-Power Non-Resistor |
| R5674-6 · R5674-7 · R5674-8 · R5674-9 · R5674-10 | NGK Racing | .460" Reach | 5/8" Hex | Tapered, Solid | V-Power Projected Non-Resistor |
| R5724-8 · R5724-9 · R5724-10 | NGK Racing | .708" Reach | 5/8" Hex | Tapered, Solid | Projected Non-Resistor |
| R6021E-9 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Loose | Fine Wire |
| R6061-8 · R6061-9 · R6061-10 · R6061-11 · R6254E-9 · R6254E-105 · R6254K-105 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Solid | Low Angle Ground Electrode Non-Resistor |
| R6252E-105 · R6252K-105 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Solid | Low Angle Ground Electrode Resistor |
| R6601-10 · R6601-11 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Semi-Surface Dis- charge Resistor |
| R6711-9 · R6711-10 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Semi-Surface Dis- charge Non-Resistor |
| R6712-9 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Loose | Surface Discharge Resistor |
| R6725-11 · R6725-105 · R6725-115 | NGK Racing | 21.5mm Reach | 13/16" Hex | Gasket, Solid | Platinum Low Angle Ground Electrode Resistor |
| R6918B-7 · R6918B-8 · R6918B-9 · R6918C-9 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Solid | Platinum Low Angle Ground Electrode Resistor |
| R7282-10 · R7282-11 · R7282-105 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Iridium, Short Resistor |
| R7282A-10 | NGK Racing | 22mm Reach | 5/8" Hex | Gasket, Solid | Iridium Low Angle Ground Electrode Short Resistor |
| R7376-8 · R7376-9 · R7376-10 | NGK Racing | 3/4" Reach | 13/16" Hex | Gasket, Solid | Iridium Low Angle Ground Electrode Resistor |
| R7420-9 · R7420-10 · R7420-11 · R7420-105 · R7440A-10L | NGK Racing | 21mm Reach | 13/16" Hex | Gasket, Solid | Iridium Low Angle Ground Electrode Resistor |
| R7433-8 · R7433-9 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Iridium ISO, Projected Resistor |
| R7434-10 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Iridium ISO, Low Angle Ground Electrode Resistor |
| R7435-9 | NGK Racing | 3/4" Reach | 5/8" Hex | Iridium, JIS, Projected | |
| R7435-10 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Iridium, JIS, Projected Resistor |
| R7436-9 · R7436-10 | NGK Racing | 3/4" Reach | 5/8" Hex | Gasket, Solid | Iridium JIS, Low Angle Ground Electrode Resistor |
| R7437-8 · R7437-9 | NGK Racing | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Iridium Projected Resistor |
| R7438-8 · R7438-9 | NGK Racing | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Iridium Low Angle Ground Electrode Resistor |
PF1/2S Spark Plugs 1 plug
| NGK plug | Range | Reach | Hex | Seat | Notes |
|---|---|---|---|---|---|
| G-2Z | Standard, non-resistor | 22.5mm Reach | 23.8mm Hex | Gasket, Stud |
Thread size not listed 9 plugs
| NGK plug | Range | Reach | Hex | Seat | Notes |
|---|---|---|---|---|---|
| FR5BHX | Ruthenium HX | 3/4" Reach | 5/8" Hex | Gasket, Solid | ISO Projected Wide Gap PSPE |
| LFER7BHX · LFR6AHX-S · LFR6BHX | Ruthenium HX | 26.5mm Reach | 5/8" Hex | Gasket, Solid | Projected, Wide Gap Dual Fine Electrode 26.5mmReach Projected PSPE |
| LFR5AHX | Ruthenium HX | 2.6mm Reach | 5/8" Hex | Gasket, Solid | Projected Dual Fine Electrode |
| LTR5AHX | Ruthenium HX | 25mm Reach | 5/8" Hex | Tapered, Solid | Projected Dual Fine Electrode |
| LTR6AHX | Ruthenium HX | 25mm Reach | 5/8" Hex | Tapered, Solid | Projected, Wide Gap Dual Fine Electrode |
| LTR6BHX · LTR7BHX | Ruthenium HX | 25mm Reach | 5/8" Hex | Tapered, Solid | Projected PSPE |
Reading the specification
Reach is the threaded length that screws into the head. Hex is the spanner size — 5/8" and 13/16" are the two common plug sockets. Seat is how the plug seals: a gasket seat uses a captive washer, a tapered seat seals on the cone and takes no washer. Solid and loose describe the gasket, and stud means the terminal nut screws off so the plug takes either a threaded or a push-on cap.
Projected means the insulator nose reaches further into the chamber, which suits engines designed for it and can foul or contact in engines that are not. Wide gap plugs come pre-gapped wider for high-energy ignition systems. Fit what the engine manufacturer specifies rather than substituting on dimensions alone.