I hand build every one of these machine moving dollies out of my home machine shop in Rittman Ohio, USA. We are a small family owned machine shop, and we specialize in making heavy duty machine moving dollies for all of your heavy equipment moving needs. These will move your Bridgeport milling machine, lathe, or any other heavy equipment up to 30,000lbs around your shop floor with ease. Or mount them permanently to add wheels to your machines. All the steel that we use is high quality, American made, and locally sourced from other small businesses here in town. The skates feature an all steel construction, and use all Grade 8 hardware for maximum strength. Each roller is precision made on the lathe, and are fully contained within the undercarriage of the skate, making them very compact, and extremely low profile. I made these skates as short as I possibly could, so that they are as easy as possible to get under your machine without having to jack the machine way high up off the floor. They only stand 1-3/4" tall, which is much lower than almost every other competing model on the market. Some of the import models are over 4 inches tall, making these ultra low profile skates much safer and easier to use. Mine also come with a mounting bolt to secure them to the bottom of your equipment, so they do not slip out when moving your valuable equipment around, which is something that is lacking on most of the commercial models. If you have any questions just ask, my name is Chris. Thanks for looking!