Not stable at all! I bought it to put on top 3D printers, however, because their head moves to print the plastic, this results in the entire shelf shaking excessively. To be honest, although it states that the weight for each shelf is up to 100 kg, seeing the construction of each shelf that looks like the back of a cabinet that we nail with nails, I personally was afraid to fill it with heavy objects so that they wouldn't come to my head! It is a cheap solution and if you want to put something not so heavy mainly for space saving, it is worth it.

As a construction, very sturdy. As for assembly, get ready for new nails because the joints are torture to fit properly. If you are prepared to be quite bothered with assembly, it is worth its money!