An efficient pulley is essential for hauling, rescue and glacier travel. The frame is heat-treated aluminum alloy, and inside a nylon pulley wheel rotates on an oil-filled bronze bearing. This item is a cosmetic second, which means it has some kind of blemish. It is still fully functional, strength-tested, and warranted. We usually cannot even tell what the blemish is, but are happy to pass our savings on this item on to you!