The Petzl Tandem Speed Double Pulley is made with stainless steel sheaves and ball bearings for excellent durability and sustained speed. Designed for Tyrolean traverses on cable or rope. Stainless steel sheaves mounted on sealed ball bearings for sustained speed, independent of person's weight, temperature, or humidity. Maximum allowable speed: 20 ms. Accepts up to three carabiners to facilitate use. Breaking strength: 24 kN. Working load: 10 kN. For use on cable 12 mm maximum diameter and rope 13 mm maximum diameter.