The SUM belay device is a new generation of belay devices designed to auto-lock when belaying a lead or top rope fall. The SUM is designed to safely belay and repel on the most popular rope diameters The SUM is specifically engineered to pick up where its competition leaves off. Ropes in the 9.1 – 10.5mm range can now be safely handled using the SUM. Thanks to its ergonomic and intuitive design, the SUM is not only safe and strong, but also easy to use. It operates smoothly and efficiently while paying out rope or taking up slack. The SUM quickly auto locks in the event of a fall