Timing belts, also known as cogged or synchronous belts, have teeth that fit into a matching toothed sheave or pulley. When correctly tensioned, they have no slippage, run at constant speed, and are often used to transfer direct motion for indexing or timing purposes. They produce less noise than chains and sprockets and do not require lubrication. Timing belts require the least maintenance of all belts and are among the most efficient.