Regardless of where you look the selection of chair mats for hard floors is very limited. Nonetheless this model is good for the price. Admittedly a rectangular (no tongue) model would be more preferred. However I found cost goes up substantially with size and shape. This is good for average sized rolling office chair.
Not really stiff and thick enough for a normal mid-thickness pile carpet. Might be OK on berber or really short pile. If you have a mid to thick pile carpet get the thicker one. Better than the thinner ones but still not enough.