I'm 5' with a 34" chest. Hanes XL girls undershirts are way too small for me (come up to my bb), but the adults are huge (stick out under my shirts). These Reebok ones fit absolutley perfectly. I'm often cold and it really helps for me to have an extra layer underneath. They have just the right amount of stretch. Also contrasting to Hanes, these aren't ribbed and the seams aren't too thick, so you can't notice them under my shirt. These are very thin though, so if you are looking to wear them by themselves, just know you'll be able to see through them.