This Hobbico Rubber Adapter (starter donut wheel) can start Glow Fuel Engines on Cars and Trucks. It is attached to a hand-held 12V electric starter w/epoxy onto the aluminum starter cone. The electric starter is switched on and inserted through the slot on the bottom of the chassis bumping up against the flywheel turning the engine over for starting. This adapter is specially designed for the Hobbico TorqMaster Starter. INCLUDES: One Rubber Adapter Donut SPECS: Inside Diameter: 1.7" (44mm) Outside Diameter: 3.9" (100mm) Thickness: 0.71" (18.1mm) AXY 5/26/93 ir/jl specs updt jxs 2/14/08