Men's Size Guide 'to fit' (chest/inches):
Age 10:27-29", Age 12:30-32", Age 14:32-34", SM:36-38", M:39-41"
LRG:41-43", XL:43-45", 2XL:46-48", 3XL:49-51"
Women's Size Guide 'to fit' (chest/inches):
Size 8:30-32",Size 10:32-34", Size 12:34-36", Size 14:36-38"
Size 16:38-40", Size 18:40-42"