The Black Raptor zip line trolley is made of powder coated steel and features hardened stainless wheels. Single ball bearings. The clip-in slot allows for the attachment of carabiners and accessories such as a handle, seat, or harness. The bottom of the trolley has open design making the installation/removal of it as easy as clipping/unclipping a carabiner. Designed for cable up to 1/2" cable in diameter and speeds in excess of 100mph