This is the Fox Pro Series #8 Long Glow Plug. This plug can be used in engines .21 size and larger. FEATURES: New high-temp seal and and heavier wire than standard plugs. Gold plated core with rhodium and platinum elements. Standard length threaded area for .21 and larger two-stroke engines. INCLUDES: One Fox Pro Series #8 Long Glow Plug with washer. REQUIRES: Installing in cylinder head of engine with plug wrench (can use HCAP2550). 1.5V Glow starter SPECS: Height: 0.75" (19mm)(including threaded area) Hex Size: 0.31" (8mm) JXS 1/04/02 ir/kh