HKS 50003-M45XL Super Fire Racing M-Series Iridium Spark Plug XL Type HR 45

Vehicle Fitment

• Universal Fit - Multiple Applications (XL Type, 12mm Thread x 26.5mm Reach)

Fitment Notes

• Universal part - no vehicle-specific fitment assignment applies
• "XL" suffix denotes a 12mm x 26.5mm thread - smaller diameter and longer reach than standard ISO 14mm plugs; confirm compatibility before ordering
• Some BMW applications (e.g., N43, N45, N55 engines) require a slim spark plug wrench for installation
• NGK equivalent: R2556G-9 - use for cross-reference verification
• Sold individually (1x per listing) - order quantity to match your engine's cylinder count

Features

• XL Type design with 12mm x 26.5mm thread suits engines requiring a narrow, long-reach plug format
• 0.6mm iridium alloy center electrode lowers voltage demand and sharpens ignition performance
• Square platinum chip on outer electrode delivers sustained durability under high combustion loads
• Short-type anti-vibration outer electrode resists tip breakage during aggressive or circuit driving
• Thermal edge design on ceramic insulator actively discharges to reduce carbon fouling buildup
• Spark support gap provides a secondary discharge zone to maintain ignition under fouled conditions
• Nickel-coated housing resists corrosion and prevents premature housing deterioration
• Suited for both stock and tuned engines requiring a colder-than-OEM heat range

Specifications

• Part Number: 50003-M45XL
• Series: Super Fire Racing M-Series
• Type: XL Type
• Center Electrode: 0.6mm Iridium Alloy
• Outer Electrode: Square Platinum Chip
• Thread Size: 12mm x 26.5mm
• Wrench Size: 16mm
• Heat Range (HKS): 45
• Heat Range Equivalent (NGK): #9 (R2556G-9)
• Heat Range Equivalent (Denso): 27

Included Components

• 1x HKS Super Fire Racing M45XL Spark Plug (10)

Product Description

The HKS Super Fire Racing M45XL is the XL Type variant of the M-Series iridium plug lineup, purpose-built for engines that require a narrower 12mm thread diameter with an extended 26.5mm reach. This configuration is distinct from the standard ISO 14mm and Long Reach (IL) variants, making it the correct choice for specific European and Japanese platforms - including select BMW (N43, N45, N55), Mitsubishi 4B11, Mercedes-Benz, and Kia applications - where the OEM plug spec calls for a 12mm thread format. The HKS heat range of 45 (NGK #9 equivalent) places this plug firmly in the performance segment, ideal for modified or boosted engines that generate excess heat beyond what a stock heat range plug can safely handle.

Like all M-Series plugs, the M45XL features a 0.6mm iridium alloy center electrode paired with a square platinum outer electrode chip, delivering strong ignition consistency, reduced misfires, and long-term durability under sustained high-load conditions. The anti-vibration short outer electrode and thermal edge insulator design keep carbon deposits in check even after extended idling or aggressive driving. Always confirm thread size (12x26.5mm) and heat range suitability before installation, and note that certain engine bays may require a slim wrench for access.