Bought this on an Instagram whim and just hoped for the best. These hand warmers are golf game changers. Simply hold the bar inside as you go to the next shot and your fingers are toasty. I could imagine that any sport that uses touch or feel with the hands would benefit from these.
Took these bad boys to Alaska for training. Kept the hands warm. Good battery on low power. Even with battery off still kept the hands warm.
I purchased a size XL vest and it fits nicely. I'm 5'11" and I weigh 214 lbs. I have plenty of room to move, it's not at all tight anywhere on my body. I can swing a golf club wearing this vest with ease. Not all clothing manufacturer's sizing is the same. Just know that who cuts the material makes a difference with any piece of clothing.