shock dr pro vs. shock dr double

which ones better? And how's come you never see guys in fights with double mouthguards? Are they not allowed?

you see guys in doubles all the time. i wear the double.

Someone just suggested this one to me.

www.opro.com

i have the double and i love it. i have met guys who love it and some who hate it. i know it takes atleast 2 weeks to adjust to it.