Wheel bearing is a generic term, including activities and fixed casters casters. Activity is what we call universal wheel casters, its structure allows for 360 degree rotation fixed casters also known as directional casters, it has no rotating structure, can't move. Usually two castors in General is with the use of, such as trolley structure is two directional wheels in the front, near the drive is two Hooke′s joints of the arm in the back round.

Fixed castors without rotating structure, can't move. Usually two castors in General is with the use of, such as the structure of the cart is in front of two fixed wheels, near the drive is two Hooke′s joints of the arm in the back round. Castors castors for a variety of materials, such as cast iron wheel, nylon wheel, and so on.