They're cheap and easy to rip. They deform if there is any weight left on them for any length of time. I made the huge mistake of buying these for gym flooring when I started out. It didn't take more than a few weeks to recognize how truly awful these things are to have around. If you have a baby who needs someplace to crawl and flop down on and around, sure, get these. If you lift weights, get your drawers on and go buy some stall mats because these don't do a dammed thing. Oh, and they're dangerous to use for like stretching, since they pull apart like a cut pizza.
Performance
Value
Build Quality