Dual positive drive belts have precision teeth on both sides improves efficiency with dual synchronous belts, this design allows more sophisticated, more efficient and more compact drives where a single belt is needed to provide accurate timing from either side, rotation direction changes or both. Dual positive drive belt can replace two or more single-sided synchronous belts, less space is needed. This reduction in space means smaller sprockets can be used, bringing the weight and component cost of the drive system down considerably, contributing to a more efficient drive system. They drop into existing trapezoidal sprockets. ContiTech Dual Hi-Performance Pd® Synchronous Belt, 136 Teeth, 3/8 in Pitch, 51 in Overall Length, 1/2 in Width, -40 to 71 °F, Chloroprene with Fiber, Fiberglass Reinforced Material, Black