This O-ring is designed for use with small engine carburetors and is made of rubber, meaning over time and further exposure to fuel, it will become brittle and crack. This O-ring is installed within the carburetor and is located between securing screws near the base. If disassembling your equipment to replace this O-ring, it is recommende...Read mored you inspect the other parts to ensure optimal performance and to prevent any leaks. Featuring an inner-diameter of approximately 0.25-inches, the replacement process for this O-ring in your engine will vary, so check the user manual for exact location of this part.