Steel wheels purchased and replaced for my safe. Doesn't matter! They roll smooth as silk and make it very easy to move a fully loaded safe (empty 1200lbs) mounted on a solid wood base uphill over cobblestones. I was impressed and wish they were available when I first built my base. I would make my life easier if I had to move my vault in the past. Come on, at least keep going, I don't have to strain my back and legs to move them again.