I am 70 years old and do not handle heat as well as I used to. The industrial vest will fit under a work shirt and depending on my activity level it will last for 1.5 to 3 hours before replacing the ice packs. The original ice packets burst thru the plastic in many areas and I hope the expensive " replacement packets are made of tougher plastic. After a summer of storage the packets need a little extra hydrating and I suppose I over hydrated them, however for the price this should have been taken into account in the manufacture of them. However even though the plastic burst, I still use them with minimal leakage because the material in the packets appears fibrous and for $50 bucks a set I will keep using them until they do not freeze any more. Some days I go thru 3 sets of 6 packets.
Since the vest is black and I work in the sun, I always wear a light colored shirt over the black vest.