Synchronous timing belts, also know as a toothed belt or synchronous belt, are designed to eliminate slippage and keep any number of objects rotating at a constant rate. Timing belts are typically made from a flexible rubber with teeth molded onto the inner surface and a cording to give the belt strength. The most common cord used in a drive belt is fiber glass, but you can also get them with kevlar or aramid fibers, steel cording and carbon fiber cording.