Rope-friendly side plates that are thick aluminum with a powder coating to enhance the life of the block. This pulley is ideal for the working arborist. Its unique upper sheave opens, closes and secures easily eliminating the chance of dropping a sheave.Comes equipped with oilite bronze bushing and with spring pin. (for 1/2" rope). Top pulley will accept up to 5/8 rope for strapping to tree.