200mm Directional lock heavy duty castors with a nylon wheel. Directional lock is a way of making a swivel castor into a fixed castor temporarily - by locking the swivel head but not the wheel which means castor moves in one direction. Directional lock castors are great for cornering or pivoting. Can be added to just one trolley wheel - usually, front left of the trolley if left cornering or front right if right cornering. 200mm Heavy Duty Nylon Castor Wheel with Directional Lock