Chin-ups work your back muscles, the back of your shoulders and arms. Dips work the pushing muscles in your arms, the front of your shoulders, and offer some chest involvement. Knee pad folds up and out of the way for unassisted training; Dip bars and straight pull-up bars fold out of the way for greater accessibility; Non-slip steps for easy access; Cold rolled steel weight stacks with noise dampening; Stainless steel guide rods resist rust and stay smooth; Kevlar belts for quiet, smooth action and optimal tensile strength; belt contains 2200 lb (998 kg) tensile strength aircraft cables.