And your undershirts, how does sizing go on those? October 05, 2021 21:26 Updated Follow Sizing is based on your chest measurement and is as follows: S: 34-36” M: 38-40” L: 42-44” XL: 44-46” 2XL: 48-50” Related articles Men's underwear sizing! Does your underwear have a fly? What’s the difference between Supersoft & Mega Soft? What's the difference between SuperFit and Cool Breeze? Do you still sell women and kid’s clothes?