I'm pretty sure these are fake or at least seconds. One of the waistbands has already come apart.  It's the second time I have gotten fake products from Amazon... starting to this I'd be better off with another distributor.
I generally wear a medium in briefs.  Size 34 waist in jeans. Never bought Calvin Klein, but haven't been missing much.  The fit was just a wee bit baggy even after a wash. Not much support up front, but the coverage in the rear is very good. Rides up a bit, but not terribly so. Material is soft enough. Rides a little higher on the waist than I expected - pictures looked more like a low rise, but these are mid-rise or higher.  These are not for sports.