The Flexwarm jacket has special heating elements built in the back, chest, and wrist areas. With the help of special sensors, you can adjust the heat output in accordance with your wishes. A useful discovery that will be appreciated not only by active sports fans.
You can find it on Amazon.com! Look in the "Sports & Outdoors" tab for "Sawyer Products B4 Extractor Pump Kit". The price right now is $16.99.