I have a pair of the Oakley Half Jackets and the fit well for me. I actually got them from my boyfriends sister because she has such a small face/head that they didn't fit her. I like them because they have enough room on the sides that I can put them over my helmet straps. If I put them under the straps they fit different and don't feel right.

The best advice I can give has already been given. Bring your helmet and try them on. Plus, I think I look totally different wearing my glasses with my helmet than without my helmet.