Don't really use them myself but I builder I work for uses one from tops tiles which comes on a mesh. Works well.
What floor covering are you going to use? Some of the mats are effected of foil underlay if you going to have laminate or wooden flooring. They can be a big problem same time! Make sure you have guaranty with the company and is good seller. You need to test them first, but if you don't have load on top they can burn out or use them on min.