Dan M.wrote a review of Castelli Flanders Warm Long-Sleeve Baselayer - Men's on June 12, 2017
Familiarity: I've used it once or twice and have initial impressions
I've got other liners that aren't biking specific but I wanted something that I could use for biking that would fit like a biking liner. I loved that this was fairly snug and that the sleeves were long enough. I often have to deal with slightly short sleeves.
Warmth was phenominal. I rode this last weekend on a night ride (12:30 - 4:00 a.m.) up to 9000 feet and it was in the mid 40s. Temp was great during the climb but I did add a windbreaker for the decent and that was enough to keep me comfortable and happy. This is exactly what I was hoping for!