HKS 50003-M45HL Super Fire Racing Iridium Spark Plug HL Type HR9 12mm x 26.5mm

Vehicle Fitment

• Universal Fit - Compatible with any vehicle requiring a 12mm x 26.5mm HL-type spark plug with Heat Range 9 (NGK equivalent) / Heat Range 27 (Denso equivalent)

Fitment Notes

• This is a universal spark plug sold individually - confirm your engine requires a 12mm x 26.5mm HL-type thread before ordering
• HL-Type uses a 12mm thread diameter with a 26.5mm long-reach length and 14mm wrench - do not confuse with the XL-Type (50003-M45XL), which shares the same 12mm x 26.5mm thread but uses a 16mm wrench; these are not interchangeable
• The 12mm thread diameter is significantly smaller than the 14mm used on JIS, ISO, G-Type, and LF-Type M-Series variants - do not interchange across thread sizes
• Heat Range 9 (NGK) / Heat Range 27 (Denso) - one step colder than the M40HL (HR8); intended for heavily tuned forced induction or race-level high-compression engines requiring maximum heat extraction
• Running Heat Range 9 on a lightly or stock-tuned engine may cause carbon fouling; confirm tune level and heat range requirements before ordering

Features

• 0.6mm Iridium Alloy Center Electrode reduces voltage requirement and delivers consistent, high-energy spark under extreme high-load and high-boost conditions
• Outer electrode incorporates a square platinum chip that improves wear resistance and boosts ignition efficiency when paired with the iridium center
• Short-type anti-vibration outer electrode is mass-reduced and shape-optimized to resist high-RPM vibration for extended service life
• Tapered outer electrode tip design maintains optimal combustion chamber space volume for improved flame kernel development
• Thermal Edge ceramic insulator actively discharges to reduce carbon deposits after prolonged idling or variable combustion conditions
• Spark Support Gap between the insulator tip and outer electrode base prevents carbon bridging and maintains reliable ignition under sustained high load
• High iridium melting point of 2,454°C tolerates elevated compression and detonation events without electrode degradation
• Nickel-coated housing resists corrosion and prevents premature housing deterioration

Specifications

• Part Number: 50003-M45HL
• Series: Super Fire Racing M-Series
• Type: HL-Type
• Heat Range: 45 (HKS) / NGK #9 equivalent / Denso #27 equivalent
• Center Electrode: 0.6mm Iridium Alloy
• Outer Electrode: Platinum Square Chip
• Thread Size: 12mm x 26.5mm
• Wrench Size: 14mm
• Sold: Individually (per piece)

Included Components

• 1x HKS Super Fire Racing M45HL Iridium Spark Plug (HL-Type)

Product Description

The HKS Super Fire Racing M45HL (50003-M45HL) is the coldest HL-Type plug in the M-Series lineup, carrying Heat Range 9 (NGK equivalent). One step colder than the M40HL (HR8), it is purpose-built for heavily boosted or race-level high-compression engines where sustained thermal load demands maximum heat extraction from the combustion chamber. The HL-Type's 12mm x 26.5mm thread and 14mm wrench size are shared with the M40HL but must not be confused with the XL-Type variants (50003-M45XL), which use the same thread dimensions but require a 16mm wrench and are therefore not interchangeable.

The M45HL's iridium alloy center electrode and platinum-tipped outer electrode deliver reliable, low-voltage spark initiation under the most demanding combustion conditions, while the Thermal Edge insulator and Spark Support Gap actively prevent carbon fouling during cool-down phases or variable combustion events. The shortened anti-vibration outer electrode maintains electrode integrity at sustained high RPM. Plugs are sold individually - confirm HL-type thread and 14mm wrench compatibility, verify your tune level warrants Heat Range 9, and order the correct quantity to match your engine's cylinder count.