I am normally a size small and based on the fit guide ordered a small. It was super small, so I exchanged it for a size medium. Just tried the medium and it’s still tight across the shoulders and chest so I will be returning. I measured the front of the jacket (size m) just under the arm pit, from one side to the other and it measured 17 inches (which says the chest on this jacket is about 34 inches). The sizing is way off!! The jacket itself is really nice but getting the right size is frustrating!

Awesome jacket! Crazy light weight, very warm, packs very small. Perfect cold weather and emergency later. Great price. Runs very fitted- I'm tiny and had to size up to a medium. I'm psyched to use this for fall riding and snow biking. The zipper on the black jacket is fluorescent yellow. When I exchanged my small for a medium I had to order 2 because a friend wanted one, too.

Living in Iowa, we can have some pretty cold temperatures in the winter time. Figuring out the right combination for layers can be tricky. What makes it more challenging is from October-April, I seem to feel cold all the time! I was intrigued by the Therminal Alpha jacket and figured it would be useful for riding but I might be able to wear it at work, too. Either way, it seemed like a solid investment piece! Recently I wore it over my Specialized Seamless LS Baselayer and went out for a ride. It was about 28 degrees. I was amazed! The jacket worked so well for my mountain bike ride. I felt warm, but never too warm- which is the goal. The breathability of the fabric is awesome. I had started out with the lightweight, non-insulated hood under my helmet. It worked slick! I hate having a ""hot head"" when I'm riding and I was able to ride a good bit before I felt like I had to take it off. It's especially helpful because I have some road riding to do before I hit singletrack. Definitely kept the abrasive wind off my ears. The nice thing with the hood is you have full mobility. It's not obtrusive or obstructive, I had the ability to turn my head both ways without feeling tangled up or restricted. I purchased the black one, unlike the photo, it does have an ion-colored zipper. I actually like that because it gives it a bit of ""pop"" rather than being straight up black. Based on my measurements, I'd be in an XS size. I purchased both a XS and a Small. It is a snug fit, and it isn't the easiest to wear over a long-sleeved baselayer because the insulation seems to want to ""grab"" the fabric. I don't have a short sleeve or tank-style baselayer to use. The small is a little more relaxed (still quite form-fitting) but figured it would be easier for me to wear at work and for layering for my commute. It's been awesome! A worthwhile investment for sure.