The Rescue Hauler (SK-710) is designed to lift heavy rescue loads under demanding conditions. It is a double 3″ pulley with a cam to prevent accidental lowering and possible shock-loading the rescue system. When the cam is in the disengaged position, it acts as a double pulley. When the cam is engaged, it allows the rope to travel in only one direction. When used with the matching double 3″ pulley (SK-712), it gives you a 4:1 mechanical advantage. Both products are anodized red in color with one black sideplate for those who want color coding to describe rigging techniques. Even the pulley sheaves are anodized to meet a 200-hour salt spray test for use in a marine environment. The cam is guaranteed for life. If you wear one out, we will replace it free. The 3″ pulleys are kinder to the rope and they prevent the rope from rubbing on the frame, which creates unnecessary friction. The frame of the Rescue Hauler is machined from extruded aircraft aluminum. This product is truly superior to all similar devices. Made in the U.S.A.