My oak desk opening was a little smaller. Had to trim a little (1/2 inch). it fits tight like i wanted. I know when I ordered it i would need to do that.
Even though the mat fits nicely under my desk the chair leaves impressions and it is hard to roll on the mat. We have a short pile carpet in our den so it is surprising that the mat sinks in so far from the chair rollers. It would be nice if there was a mat the same size with a thicker construction.
My last mat was nicer. It eventually cracked so I had to get a new one. This one is a bit too short and too thin. It's okay for the home but is not adequate for a true office.