Very sturdy and customizable, we love the product so far. The plastic covers for the tops and bottoms of the frame are somewhat difficult to put on, some may break. The hammer issued with the product is weak and breaks apart. You need quite a bit of force to get the shelves together, which was somewhat difficult. I took it as a positive sign that the unit would not come apart once put together; unless forcibly taken apart with a rubber mallet again. The bottoms do not have adjusters, so floor must be level. I made the mistake of not checking beforehand. However, the unit is very sturdy so unless you make it extremely top heavy, I do not believe it will tip over. We love the product, we house our reptiles in 120gal, and a 40gal, and have our flat screen on the top shelf. We have room to grow still. So overall, product is great!