Easy installation, just bolt on existing wood rails or motor mount for glow engines. Also suitable as additional Heat Sink. 20mm Size: Hacker B20, Himaxx HA 2015/2025, Razor motors 28mm Size: Mega 16/x/x, Speed 400 motors 36mm Size: Hacker B50, Mega 22/x/x, Jeti 15-30-45/x motors Requires Foam Tape Cushioning.