I bought two of these for my large cat to (1) sun in a window, and also (2)  to give a boost to a higher perch.  They mostly work for these purposes and they were simple to assemble, not requiring any additional tools.  Only complaints are that they are not solidly stable, having a relatively small base for the height and weight, especially for a jumping LARGE cat, and they don't have logistical stepping areas for the cat to get to the top perch.  This also ties into the not stable comment.  My cat went into the cabin area when it was still on the floor, prior to assembly, but doesn't use it much now that it's higher.  We'll see how that goes.