Each of the dual wheels is 2" in diameter and 3/4" in width.
The caster body is a composite plastic. The caster tread is thermoplastic rubber and the caster core is polypropylene plastic. The caster axle is steel as is the 360 degree swiveling socket stem.
Each caster can support up to 150 lbs. Four casters together could support up to 4 x 150 lbs. = 600 lbs.