I debated on size. Went with a large over a medium and was glad I did. Aero stuff fits a bit tight and I was concerned putting it on that it was still a bit small. Once out on the bike and run, I was thrilled. I have not swam in it yet, but believe it will be great there too. Neck scoops a bit lower than I am used to, but forgot about it once I got going. Very nice, Zoot!