Turn up the climate control on the coldest days with highly-breathable, heavyweight fleece top.
Did someone call for climate control? This men's Burton Heavyweight X Base Layer Quarter-Zip will do the work. Highly breathable, heavyweight fleece keeps you cozy even on the coldest of mountain days, and four-way stretch works to give you all the flexibility you need for a solid day of riding. Bonus: you can still keep your friends close, thanks to the stink-resistant finish. (You're welcome for that one.)