Snug fit with a elastic in the hem
This is my second long sleeved rash guard from Raven Fight Wear. The first shirt I've been using once a week in an open mat under the gi or nogi. The quality is very good. It doesn't have much wear and tear even though I've rough housed in it over two years now in sweaty conditions.
The Aerial Assault pattern is lovely. The Raven logo on the left side of the chest tends to crawl into my armpit. I got size medium and it fits nice and snug (178cm, 150lb, 32c).
There is a ton a of rash guard options in the market. If you are having hard times to choose which long sleeve to get, invest in Raven.