This is the Fox Pro Series #8 Short Glow Plug. This plug can be used in engines smaller than .21 size. FEATURES: New high-temp seal and and heavier wire than standard plugs. Gold plated core with rhodium and platinum elements. Shortened threaded area does not get in the way of the piston in smaller engines. INCLUDES: One Fox Pro Series #8 Short Glow Plug with washer. REQUIRES: Installing in cylinder head of engine with plug wrench (can use HCAP2550). 1.5V Glow starter SPECS: Height: 0.63" (16mm)(including threaded area) Hex Size: 0.31" (8mm) JXS 1/04/02 ir/kh