A pulley ( also called a block and tackle) is a mechanism composed of a wheel ( called a sheave) with a groove between two flanges around the wheel' s circumference. A rope, cable , belt or chain usually runs inside the groove. Pulleys are used to change the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in either a linear or rotational system of motion. - Twin Roll # 827 - Extra Roll # 820 - Pamir Fast # 826 - Block Roll # 818