I bought one of these in navy color originally in a large, and it was too tight so I exchanged it for extra large, while at the same time ordering a heather gray one. Those two came in and the navy extra large fit fine, but I was swimming in the extra large heather gray one. Turns out the heather colors are a cotton/poly blend, while the solid colors are all cotton, and as such they fit differently. In short, the heather colors are a bot looser than the solid ones.
Rating: [4 of 5 Stars!]