This is the 5/16-24 Jam Nut (Short) & 8mm Bushing Adapter Kit from Tru-Turn. FEATURES: Steel construction. Tapped 10-32 for cone screw. Used to mount Tru-Turn aluminum spinners onto the following engines: OS Max .70-1.20 Surpass 4-Stroke Abitar 1.20 4-Stroke OS Max .91FX and 1.40 RX OS FS-91 INCLUDES: One Short Adapter Jam Nut One Aluminum Bushing REQUIRES: 1/2" End Wrench To Tighten Tru Turn Aluminum Spinner SPECS: Crankshaft Thread Size: 5/16" - 24 Spinner Mounting Bolt Thread Size: 10-32 Bushing Size: Inner: 8mm Outer: 3/8" JAL 5/19/99 ir/jl