4pcs U Type Groove Pulley, Pulley Rolling Bearing Roller Guide U Groove Wheel for Doors, Windows, Driving Mechanical Equipment, 8 x 40 x 20mm / 0.3 x 1.6 x 0.8in
【WIDELY USED】Widely used in doors and windows to track and drive mechanical equipments. These gadgets can be used to build the track system or replace the wheels on the dolly.