I think that they serve the purpose well but a little harder plastic would keep the chair from "settleing" into a little "hole" while sitting still. It is a little effort to get the chair to move out of that "hole"!
Slides back and forth too much with the chair movement. It is on a low pile carpet and the bottom groves do not hold it in place. Already making dimples in 4 places with chair wheels. Kind of disappointed. But will give 3 star. Very smooth surface looks neat and nice. Fast delivery. Delivered as a roll. Stayed flat immediately after unrolled.