O'Neill Men's Comp Vest Size Chart

How to measure:
  1. Chest: With your arms relaxed by your side, measure around the fullest part of your chest.

If your measurements border on the top end of your chosen size, go for the next size up.

SIZE CHEST (in)
XS 35 - 38" 
S 37 - 40"
M 38 - 42"
L 40 - 44"
XL 43 - 47"
2XL 46 - 50"
3XL 48 - 52"