This is a genuine throttle return spring used on select small engines. The throttle return spring is part of the throttle system. It is attached to the throttle cable and the throttle body or carburetor, and is responsible for pushing the throttle closed when the gas is released and opening the throttle when the throttle trigger is engaged. If the spring is faulty, the throttle will not be able to open and close properly. This can affect the machine's ability to operate and even prevent it from operating at all if the throttle remains closed and no power can get through. A replacement should be done as soon as possible to prevent further damage to the engine. This genuine OEM throttle return spring is manufactured by Tecumseh, and compatible with machines from Toro, Husqvarna, MTD, Lawn Boy, and Tecumseh. There are over 150 models that can use this replacement part. It is made of durable metal and sold as an individual part. This throttle return spring is a simple replacement that should only take a few minutes. Be sure to use care when replacing the spring because it can be susceptible to damage under excessive pressure or strain.