Manufactured from 1/8" steel with grommets to hold 1/4" steel floor wheels. Ground wheel axle bolts are fully threaded bolts, not shank or shoulder bolts, so you'll need to visit a hardware store if you want to replace them, especially with pre-installed "nylon" wheels. The tire rollers are heavy, appear to be well constructed and really help rotate the tire to align with the threaded lugs. The lugs holding the bottom rollers are not evenly spaced - wrong inside diameter/wrong welded. The pre-assembled wheel/castor axle bolt has a raised thread on one side and a slightly recessed thread on the other side of the self-locking nut, which doesn't bother too much. Used when replacing 20" summer tires with front rim winter tires on the Ram 1500 P/U. Simply pick up the tire and then lean/tilt it against the rack handle for transport to the P/U. I sat behind this structure in an office wheelchair. You need to make it perfectly perpendicular to the bolt pattern, not left or right of it, and then also rotate where the rim bolt holes line up. Once you get the hang of it, squeeze the handle to raise the tire if necessary, and keep your foot steady as you press the tire and rim onto the lugs to do the trick. Former engine mechanic, 67, like the others back pain.