Bearing in mind the current weather and a previous posting on heatsroke I thought I would chip in with my feelings on the these items. I originally starting using a cooling vest while riding in the Philippines in temperatures similar to those we are having here at the moment. The model I chose was a bargain basement $39.00 Techniche model on mail order from the States. It works on the principle of soaking up water and then evaporating it off and cooling you down whilst doing so. All that needed doing was to soak it in water for a few minutes, shake off the excess water and wear it, either next to the skin or over a t shirt and under mesh outer jacket. Depending on the ambient humidity, that was usually good for about 2 - 3 hrs before repeating the exercise. This is a marvellous piece of kit as it keeps you from overheating and dehydrating even under extreme heat conditions and allows you to feel pretty comfortable all in all. My only criticism of this particular model was that it felt a tad clammy when initially put on but nevertheless a small price to pay. Recently I decided to splurge out and bought a US$90.00 Silver Eagle cooling jacket from coolingapparel.com This model has all the benefits off the cheaper model but is of far better build quality and pretty much stays dry from the off, so no claminess to contend with. I personally swear by this piece of kit and reckon it is one of the best pieces of kit in my wardrobe for these conditions. I would only add that they might not be as effective under full leathers as they require an airflow to produce the required evaporation. A lifesaver in extreme heat conditions!