I'm 5'5", 125lbs, 36c, 4/6 jeans and ordered a medium. It fits snug, there is no spare room, especially in the chest area. It is a thick flannel material with a mesh liner, doesn't breathe quite like a mesh jacket, but it isn't suffocating either. The chest pockets can fit a license & credit card. There are extra material tabs on the shoulders (military-style) that snaps near the collar that I cut off completely. The tabs made me look like a linebacker. The back of the shirt is longer so I don't have to worry about it riding up. Overall I love this shirt and have worn out in up to 95 degree weather.