ENORMOUS. A bobcat could use this thing. My cats are slowly starting to run on it, but my cats’ claws constantly snag on the carpet even after trimming. I wish this came with a smooth surface option. Anyway, it took about 4-5 hours to put together, which was pretty easy (definitely get a power screwdriver). It seems very solid, but it is LOUD when the cats walk or run on it. I think I’ll keep it. I’m going to try to find something to cover the carpet track with, because I think my cats would love it if they didn’t keep getting their claws snagged.