The Kwik-Stop is an unbelievable product. It is unbelievable because it solves one of the most obvious problems with R/C cars. Shutting off the engine. In the past, you would pinch the fuel line, put a rag in the exhaust pipe, or use your finger. This works, but what if the engine is hot or if you have to remove the body to get at the fuel line. The Kwik-Stop simply inserts into the exhaust pipe opening and shuts off the engine instantly. Available in 7 hot colors.