Model in photo is 40" chest and wearing size large
SIZE CHART
Small fit to chest = 35-37 inches
Medium fit to chest = 37-39 inches
Large fit to chest = 39-41 inches
XL fit to chest = 41-43 inches
2XL fit to chest = 43-45 inches
3XL fit to chest = 45-47 inches
4XL fit to chest = 47-49 inches