English: A toothed rubber timing belt, also known as a synchronous belt, is a crucial component in an internal combustion engine. It is made of durable rubber and features teeth on its inner surface that mesh with corresponding grooves on the crankshaft and camshaft pulleys. These teeth ensure precise synchronization between the rotation of the crankshaft and camshaft, which is essential for the correct timing of the engine’s valves in relation to the movement of the pistons.