The DMM Revolver Locksafe carabiner is now a well established piece of kit for arborist climbing systems. Designed by the Treemagineers, the DMM Revolver is one of the only 'biners on the market to be certified both as a carabiner and a pulley. It uses rolling friction rather than sliding friction of the rope over the bar. The rope rolls over the pulley wheel on the DMM Revolver which means less friction. Less friction translates to less force holding the climber back, which makes upward (or branch walking) progress a lot easier (and quicker). Another benefit of less friction is reduced wear and tear on your rope - increasing the ropes working life considerably. Great for re-directs.