To start, I like the box. I have had it just over a year($117 then) and use it 3-4 times a week. It has held up very well. The vinyl and zippers are intact but showing some wear. Seems very durable and the foam feels about like it did when new. It’s never been left out in the weather or thrown around so might be why it’s still in good shape.As far as stability, it’s a foam box and does compress under load. I have noticed if I land with lots of forward motion, the leading edge on the floor will compress and feel like it’s going to roll out from under me. Granted it’s only happened when jumping the 30”. Tje other two heights are fine. It’s probably more of how I’m landing, but still something to think about.I truly feel it’s a good price too. Even at $140, it’s not bad. A sheet of 3/4” plywood here in Texas will cost me $60 . Then I have to build it.Basically, I’d buy this box again. It’s been good to have. Easy to move, easy to use and makes a soft chair after a workout.Just buy one, you’ll like it.