I'm not using these as jump boxes. They're serving a wide variety of other purposes from assisting with other exercises to being used as stools while painting to the 12-in being used as a step stool. And I'm happy with them for these purposes.Not sure if I would be having paid full price though as I got a used set for more than 50% off. To my surprise, the reported damage was minor tearing of the top material. A bit of gorilla tape fixed them right up to prevent further damage, and I might either replace the tops with thicker plywood or cover them with proper rubber-like padding in the future anyway. So totally worth it for the savings.They seem quite sturdy. The 30-in one squeaks and creaks quite a bit, but I think it'll hold up fine. Probably just from having longer legs. The others seem quiet and firm. No stability issues that I've seen.Sturdy, balanced without any teetering. Would recommend.Best purchase I have boughtI bought the 12-inch and 18-inch. Both items arrived with legs bubble wrapped, completely scratch-free. They are sturdy and can be used for many different exercises. The 18-inch arrived with some kind of dusty brownish powder coating on the legs and rubberized feet. I wiped it off easily with rubbing alcohol and paper towels. The 12-inch arrived without that dusty coating. I'm pleased with my purchases and feel comfortable recommending this box to others.It was a little smaller than I was hoping but that was my error. The box is sturdy with a welded frame and should handle most of what the average person can throw at it. Not a bad purchase.Very sturdy, solid. Perfect for sturdy step box, very happy with purchase!GreaaTPerfect for various training purposesFor the price this is a great plyo box . Definitely recommend