Received the jacket today from Backcountry (thx for the 2 day free shipping) and wore it on a 42F day for my favorite single track trail in MN. I only used a compression shirt along with this jacket and it was plenty warm The jacket is incredibly light and super breathable. The Windstopper Active shell did a great job blocking out the windchill. My body was pretty much dry after an 11 mile of intense, technical ride. FYI, I'm 5"6, 150 lbs with a 37.5" chest and a Large fits almost perfectly. The sleeves are a bit long but when in riding position,they fit very well. This is a great jacket and well worth the price.