These things are HEAVY! They come in a small wooden crate that weighed over 100lbs, delivered by UPS. It's pretty stunning that they can make this things in China, ship them to the USA on a cargo ship, truck them around the country, and deliver them to my door for the price they do. The quality of the wheel bearings and rotary plate seem fine for moderate use. This style of machine skate can be tricky to use depending on your application. It's not always easy to keep them in place under a machine, especially if the floor is uneven. Three tends to be more stable than four, but that won't work for every piece of equipment. I moved a 2000lb Bridgeport mill off of a pallet jack and into final position by myself with these skates, some wood blocks, and a toe jack. I'll be hanging on to them for future machinery moving tasks.
Ramon Tapia 
Eddie 
