Bought a large amount of these. No problem at all. Parked a broadcast truck on them, all good. Ran 200 ft no problem and stay put on all surface,never slide. Thy work as well as our expensive ones, but you have to use your brain when using any type. They do have limitation and you need to understand weigh has to be spread out, not all in one spot. They need to be layer out straight. If you arch them, you will run into issues.In our opinion, these are one of the best buys out there, but do keep in mind they are $20, not $100 Well worth the money