The momentary switch is a part that is unique to self-propelled lawn mowers and used to control the power of the self-propelled movement. The momentary switch provides power when pressed and held, and will ensure that the unit operates properly while in use. Over time, the momentary switch can become worn, short out, or just stop working as it should. This will require a replacement with a compatible part or the self-propelled part of the machine will not work properly. This genuine OEM part is compatible with self-propelled mowers from Cub Cadet, Bolens, MTD, Murray, and Troy-Bilt. It is made of durable materials and sold individually. Replacing this switch requires a wrench and screwdriver, as well as a socket set. Without a self-propelled switch, the mower will still operate but it will require the user to push the machine with their entire body weight. This can make the process of mowing much more difficult and often cause further unnecessary wear to the machine, which is why a replacement is essential.