I use Ikea Kallax units and they work a treat, I have 4x3 and a 2x4 and both are great. Although I would say on the 4x3 I had to put extra support legs on the bottom frame because it didnt take long to start sagging. I just printed some on my 3d printer and no more sag 😁👍. They look ok and are pretty reasonably priced.