Strong and holds a lot of weight.
Your review: Great shelves once they are assembled. There are issues about where to put the cross bars for stability, but these are strong and functional. You won't need to replace them down the road.
Pros: Strong, can be tweaked for shelf height easily to add variety. Once anchored to another shelf, extremely strong and safe compared to past shelves we have used.
Cons: Harder to assemble than it would seem. If the cross bar isn't perfect, they can easily shift before they are completely anchored to each other. If you are moving them from one place to another, the drop in shelves can fall and the whole thing can fall apart. So be careful to not lose the shelves when moving.