The Genuine BMW Engine Coolant Bypass Pipe O-Ring - 11531435808 is a small circular rubber ring that is used to seal the connection between the engine coolant bypass pipe and the engine block. This O-ring is an essential component in the cooling system of a BMW vehicle, as it helps to prevent any leaks or loss of coolant. It is made from high-quality materials and is designed to withstand the extreme temperatures and pressures of the engine. This Genuine BMW O-ring is a direct replacement for the original part and is compatible with a wide range of BMW models. It is a reliable and durable solution for maintaining the proper functioning of the engine's cooling system.