If you are looking for a high-performance trolley with an added safety feature, the ZLP Torpedo is it. It is made of stainless steel side plates and features hardened stainless wheels. Each wheel is equipped with two ball bearings giving it a fast smooth ride, and ensures peak performance and extended life. The clip-in slot allows for the use of 3 carabiners to attach accessories such as a handle, seat or harness. There is also a clip-in slot to attach a carabiner above the cable as an added safety back-up feature. The bottom of the trolley has an open design making installation and removal from the cable as easy as clipping or unclipping a carabiner. Designed for cable up to 1/2″ in diameter.