Before I had a square 36"x48" mat. I wanted the lip so that I wouldn't roll off the front of the mat. However I found that the lip on this mat counts against the 48" and I was rolling off the back of the mat. Personal preference but I'd rather roll of the front and I returned it. Everything else was fine.
Don't waste your money on this chair mat. It curls up and then its hard to roll your chair over it. I have had to set heavy boxes on the corners to hold them down but it hasn't helped. By the time I realized that it was just not going to work no matter what I did and wanted to return it I had exceeded the time limit on returns.
This mat is the same size as the one I had previously. However when I roll my chair off of the mat - the wheels gets caught on the end of the mat when I try to roll it back on. I exercise every morning and it becomes a challenge to lift my chair back onto the mat. I had purchased my previously mat from staples however it was a heavier/harder quality. On this mat I see the imprint of the wheels into the mat. I think the quality of the mat has been compromised.