Muscle Rack 5-Shelf Steel Storage Shelf Unit, Black, 4000 lbs Capacity

Good solid shelf once assembled. Easy to follow instructions. Decent size for not a lot of money. Very pleased with the purchase, bought me a second one.

This shelf system seems to be well made and sturdy. The interlocking tab & slot design relies on gravity and/or the weight of materials placed on shelving to provide strength. As others have said, the design for placing upper legs atop lower legs is quite difficult to do alone. I found it easier to build the two halves and then set the upper on top of the lower. Of course, that requires a second set of hands but does get thing done quickly. The puny particle board shelving appeared to be a joke when first noticing it's thickness (or significant lack thereof). But boy can that baby hold some weight! So, don't judge the shelving until you've had a chance to try it out. I purchased one for a beta test and was so impressed that I've since purchased 15 more to complete my storage requirement.