1/4-20 x 1/2 in.
. per caster Dynamic rating: 49lbs/wheel, 196lbs/set of 4, Static Rating : 75lbs/wheel, 300bs/set of 4 and assures that your wheels will not warp or crack under pressure. twin wheels allow for more surface area in contact with the floor and move in opposite directions to minimize carpet fiber twisting. 2 in.