CMI® Rapid Transit Trolley Pulley is of the highest quality and obtains excellent performance as a zip line trolley. This trolley is very similar to CMI’s Micro Trolley, but features larger wheels, bearings and no rear backup. The top tie-in hole means that it is easy to set up the Rapid Transit Trolley on a piggyback or dual cable systems. The Rapid Transit Trolley features stainless steel side plates, two 2" stainless steel sheaves, bearing, and a stainless steel axle.