Seems pretty sturdy once built. The metal is kind of thin so be careful. It bends rather easily if you don't line up the two tabs on either side perfectly. The shelves may hold up to 1,000 pounds, but when I kneeled on one (because I'm short) to build up for the 4th shelf, I heard a slight crack sound. When I looked under, I can see a slight bend/break from where my knee was on the other side. I wouldn't even think that this would happen for a shelf that can hold 1000lbs.