3″ Low Profile Polyolefin Rigid Caster W Top Plate Chrome Wheel Diameter : 3 Tread Width : 1.25 Wheel Type : — Core Detail : — Wheel Color : Black Bearing Type : Delrin Bearing Fastening Type : Plate Fastening Size : 3-5/8″ X 2-1/2″ Mounting Bolt Diameter : — Capacity : — Mount Height : — &Nbsp; Rigid Casters A Basic, Rigid Caster Consists Of A Wheel Mounted To A Stationary Fork. The Orientation Of The Fork, Which Is Fixed Relative To The Vehicle, Is Determined When The Caster Is Mounted To The Vehicle. An Example Of This Is The Wheels Found At The Rear Of A Shopping Cart In North America. Rigid Casters Tend To Restrict Vehicle Motion So That The Vehicle Travels Along A Straight Line