Check the listing for details. MADE IN USA 18,000lb Machine Moving Skate Dolly Roller Set (4). Condition: New. Listed at 225.00 USD. Machine Skate, 4 piece Set, Bridgeport Mover, 9 ton as a set, USA made. Condition is New. This is a set of 4 skates. We buy bearings in the hundreds and US steel in 20' sticks to keep our cost as low as possible. The other skates on eBay are inferior Chinese steel and are completely subsidized by the Communist party. These are made in the USA, 5" long, 5.5" wide and 1.7" tall. 1/2-13 thread in the center to allow skate to be bolted to machine and turned by a crowbar to steer machine around the shop. Rating of 3 ton a skate uniform load. Loads can spike on uneven floors so use caution when moving machines. Since even concrete is not level often only 3 skates are carrying the load even in 4 are used which is why we derate the skates as a set. Ratings are based on uniform static bearing load which is 50% of dynamic load. We are not repondsible for damage due to skate failure since we never provide individual guidance on use. Specifications are based on bearing static load ratings. No specification or engineering documentation is available.