This is the most helpful piece of furniture that I've bought in a very long time. It holds so much inside. I put a foldable shelf organizer in the top half to double the space for multiple toiletries and in the bottom half I installed an acrylic floating half-shelf that I had left over from another project to hold medicine bottles and other small items. It is very spacious without adding the stacking units inside, but doing so increased the amount of real estate available and helped get rid of all the clutter on the bathroom counter.  Even full of toiletries the unit is very stable without being attached to the wall, though attaching would be recommended.