so I originally bought the jacket in a size small because I went off of their sizing guide and unless you want to wear the jacket with nothing else underneath the small fits. but even having a thin t-shirt on I had a hard time moving. Customer service is great. they exchanged my small for a medium and I love love love, love my new jacket! The battery works fantastic. it keeps me warm. when my hands go in the pocket it warms up my hands. I love the low medium in high settings. I will be purchasing the vest next! I am hoping the size the socks smaller because the reviews on the socks I hear run big so I'm hoping they fix that because after the vest I want to buy the heated socks! I love this jacket.