ACDelco GM Original Equipment Multi-Purpose O-Rings are used in some applications instead of paper or composite gaskets to seal engine components. The interface between components will have a machined groove to accept the O-ring. The O-ring is slightly compressed when assembled to provide a liquid-tight seal, keeping engine fluids in and air and dirt out. These original equipment O-rings have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.