My first concern before ordering these was "what size is a Sm/Med"? Answer: these are closer to a Med than a Sm. I don't think they could have fit any better. The opening in the front is just the right size. It let all my junk hang out! Not too sure about the rear opening. I suppose if we were more into anal play, it would be a huge benefit. I have several pair of open underwear...and this has moved close to the top of the list. I do wish things like this for men came in more styles and colors. Oh, yeah...my wife was impressed with them, too!