I really want to like this bra but the sizing on these seems off.  I purchased a 5X from a store and it seemed too tight.  It's the gray "private jet" color and the band at the bottom is thicker and it overall seems better quality than this one.  When I purchased the 5X, a 6X wasn't an option listed.  When I received this 6X, I could tell it was much larger than the 5X, the material seemed thinner quality and the band was not as thick.  Because it's larger, it doesn't provide great support and because the band is thinner/looser, it rolls up worse than the 5X did.  It may be a difference in fabric as the gray 5X is patterned and the black 6X is not.  The black is the only one available in a 6X (when I purchased) so there's definitely something different.  These bras are for comfort and not really support so if you need something to wear under casual clothes just for a bit of modesty and to have something on, then I would recommend ordering according to your size and giving it a try.  I can actually wear the 5X and 6X but the 5X is more snug- a little harder to get on, but provides a better fit once I get it on.  If you're in between a size, I would order the smaller one.