The only singlehanded bosun's chair that allows you to work ABOVE the masthead without leaving the chair.The only bosuns chair that allows solo, unassisted ascents of the mast, the Mastclimber fits over any taut 3/8" to 5/8" rope halyard. Constructed from 1 1/2" ballistic nylon webbing with a fiberglass-reinforced seat,Mastclimber combines:A bosuns chair with backrestLeg straps with a pair of one-way anodized aluminum/stainless jammers, located at the chair seat and the intersection of the leg strapsClimb the mast quickly and safely using only leg muscles. With no need for static lines, the easy-to-use climber is operated by alternatively standing up on the leg straps, which allows you to slide up the one-way jammer of the bosuns chair. To descend the mast, the procedure is reversed. Recommended by Practical Sailor in June 2010. Maximum waist size 50".Check out our West Advisor video on MastclimberSee how a rigging professional uses the Mastclimber to safely and easily ascend the mast, as West Marine's Mark Chandler demonstrates this product in our West Advisor Video, Climbing Your Sailboats Rig with the ATN Mastclimber.