purchased this to put under treadmill and weight set (works great), and the kids loved it, and wanted it in their rooms, so I ordered several different colors, and let them mix/match to their liking. After placing 3 or 4 tiles (they interlock easily and securely), realized that the strong plastic smell was a problem. I left them in the garage with the windows open for a week or so, and the aroma went away mostly (may want to wait until open window weather arrives). We have used them on top of concrete, veneer "wood" flooring (where they are great sound insulators), and in one room on top of some gruesome shag carpet, where they work very well, and have some extra spring, but we do have the occasional shag fiber pop up through the seams. The are tough to sweep, but vacuum up easily with the beater bar turned off (or they get scratched)-would have been 5 stars but for the initial smell.
Buy 3/8 inch Puzzle-Lock Interlocking Rubber Mats - 10 tiles per box - 28 sq/ft coverage!