Ladies sizes to fit bust:
S: 34 inches / 86 cm
M: 36 inches / 91 cm
L: 40 inches / 102 cm

Mens sizes to fit chest:
M: 40 inches / 102 cm
L: 42 inches / 1007 cm
XL: 44 inches / 112 cm

Also includes Child sizes for ages 4-13