Slipstick CB420 Carpet Protector Caster Cups / Carpet Grippers for Under Furniture (Set of 4) 2-1/4 Inch - Clear Plastic Prevents bed roller wheels from indenting and damaging carpet or thick rugs Designed for wheels 2 inches (50 mm) in diameter x 2-1/4 inches (56mm) wide or smaller Unique spike design disperses weight evenly across carpeted surface Deep cup design cradles bed frame caster wheels and prevents movement Clear design makes product appear invisible when in use