The patented extruded hole design, in conjunction with the groove profile of the sheave, provides a more powerful grip than conventional designs - up to 20:1 holding power. Unrivalled low weight is achieved by the use of a Torlon^® ratchet pawl, high grade machined alloy sheave and black Acetal hubs and bearings. On-Off switching knob is fitted to both sides of the swivel blocks (one can be removed if desired). Ratchet blocks can be disassembled for sheave replacement with RF62000.