ordered a "mat" thought they were all the same!! Well they are not! There are mats for different thicknesses of carpet mats for different hard surfaces. Bottom line now I have a "used"mat that does not work. In addition we have to get the proper mat! Hopefully I ordered the mat for the correct thickness of carpet(which I measured with my trusty paper clip) as shown in a diagram!! My advise is categorize the mats according to what kind of flooring they will be used on and of course dimensions and shape.