Here’s the lowdown on our caster. We have now sold in excess of 400,000 of these. This wheel is heavy duty. Works very nicely in highly demanding rental operations. The stem of this caster wheel is 1.375″ OD (#6 tube) with a 4 inch length. It has a double safety margin built into the load rating. Our wheel is heavy duty, load tested to handle 500 lb with an 8-to-1 safety margin. It’s cast iron frame has a rubber exterior that is two inches wide and over an inch thick. There are ball bearings in the pivot mechanism to handle high loading. It’s double locking, so the wheel cannot turn or rotate when locked. Finally, it’s fitted with two zinc-plated grease fittings to keep things rolling smoothly.