These are positively heavy duty! Solid cast iron wheels are very sturdy, and the poly wrap around them are non-marring. They work very well. Only one issue that I had with them was the locking pin holes didn't line up. It was close, but using a 3/8\" diameter pin would not work. Possible that a 1/4\" pin might work. I had to ream the holes with a drill to remedy the situation... No big deal. All in all a very solid product.