These O rings are replacement parts intended for use in a number of gasoline-powered lawn trimmers. The O rings serve as gaskets and are placed at the entry and exit points in the carburetors where gasoline and air are mixed and the expansion powers the trimmer. Though constructed of durable material, periodically the flow of the air/fuel mix or the rush of expanding air will cause damage to occur to the O rings so they become less resilient and the carburetor functions less efficiently. In these cases, users often decide to replace not just the element of the carburetor but the O rings as well. Users may notice problems with the carburetor when they cannot get an adequate adjustment, allowing the trimmer to function smoothly. They may also have trouble getting the trimmers to start at all or run without smoking. To replace the O rings, remove the air filter cover and carburetor. Once the carburetor has been cleaned, and the gasket and filter replaced, add a fresh mix of 40:1 fuel. The trimmer should start immediately. These OEM certified O rings are compatible with Bolens, Troy-Bilt, Yard Machines, and Craftsmen trimmers.