Perfect for triathlon and all the elements that make up the tri. The mesh panels are exquisite quality and help to keep you cool and dry. The fabric will dry quickly after the swim and there are two good pockets to stash gels for the bike and run. The front zip has good length providing ventilation and easy on off. A medium equates to a size 12. When looking for a bra to wear with this tank, we would recommend looking at bras that are single layers of fabric, so that when the bra gets wet it will dry quickly, good examples are the ShockAbsorber B518 and B972.