The Reinz Fuel Pressure Regulator O-Ring is a small rubber ring with a diameter of 20mm and a thickness of 2.5mm. It is designed to be used in fuel pressure regulators, which are responsible for maintaining a consistent and safe fuel pressure in a vehicle's fuel system. This O-ring helps to create a tight seal between the fuel pressure regulator and other components, preventing fuel leaks and ensuring proper functioning of the system. It is a genuine Reinz product, known for its high quality and durability.