Purchased the heated sweatshirt to wear under my jacket. Work outside and can be standing for 8 hours or more. Charged battery and placed It in the back of the sweatshirt pocket. The temperature was 18 degrees the day I wore it. Warms the core of your body just enough. Only problem the battery does not last that long when used on high temp mode, luckily I purchased 2 extra batteries all three lasted me about 9 hours.
Purchased for my husband who works outside (electrical work). He wore it the first time to a race and was amazed how well it kept him warm...he can't wait to actually use it for work. Says the battery located in the back of the sweatshirt is great because it doesn't get in the way of your arms or hands. The weight of the battery is good and light.
I haven't had a chance to test it out since its been over a 100 most days. I plan to put under a real jacket while hunting in tree stand for days when it's below freezing.