There is a part inside the internal combustion engine named camshaft. The camshaft, as a cylinder, is to align with the engine's cylinder and make it possible for the engine's valve to open and close. The camshaft is attached to the engine's crankshaft by the timing belt. The camshaft, working along with the timing belt, opens the valves in coordination with the stroking of the pistons. Owing to the cooperation of the camshaft and the timing belt, you need to make sure either of them is working properly. Otherwise, the system will stop working and cause damage to the engine. For most BMW modern cars, they have dual overhead camshafts, with one for exhaust valves and one for intake valves. Check you camshaft regularly and once you decide to change it, we are glad to be your first choice for your BMW genuine OEM camshaft. We offer you the high quality product with an affordable price.