Billabong solar heart system 3mm thickness with 2mm or 1.5mm on the arms. Off-the-rack ML size. Used for two seasons. The jersey is very soft, and there's no water entry from the crotch, etc., so you can continue to use it comfortably. Back zip, so you can adjust it to fit your neck. I'm selling it because I've gained weight. No price reductions. Please understand that this is a used item.