The extension spring is compatible with many lawn tractor and riding mower models. The extension spring is often used to allow the idler pulley bracket to pivot when the blade rotation is started or turned off. If there is a problem with the spring, it will affect the functionality and usability of the mower.The spring is made from quality metal, and it is built to stand up to the elements. However, there is still the possibility of problems with the extension spring. In some cases, it might become worn out over time and need to be replaced. It might also corrode. When owners are working on other parts of the machine, the spring could become lost if they remove it.The extension spring will work with select lawn tractors from MTD, Yard Machines, Yard-Man, Troy-Bilt, and Husky. The spring is sold individually. It is an authentic OEM replacement part sourced from the manufacturer.