This very large mat is perfect behind my client’s desk. He rolls his chair from side-to-side to reach files and the shredder. His chair rolls easily and the mat stays put in the no-pile carpet.
I got the Staples Medium Pile Chair May because I just got new carpeting and didn’t want it snagged by the mat. Unlike the low pile mats this one doesn’t have sharp points but rounded nubs. It holds onto the carpet just as well but doesn’t pull threads. It’s a little narrower than I needed (I roll around a bit when I’m working) but I didn’t have room for the next size up.