Singing Rock Pulley TandemDouble pulley for Tyrolean traverses and zip lines with two stainless steel sheaves each sheave is equipped with a pair of sealed ball bearings for great durability hard aluminium alloy body is black anodized and protects the sheaves from damage large attachment point can accommodate up to three carabiners second attachment point for a back up carabiner or tackle systems building two sheaves prevent from twisting, thus providing a smooth and more