Like an inside-out soft shell.
Verified Buyer Reviewed by Howell Devine fan from California on Friday, March 9, 2018
The lining of the sleeve is slick and satiny. The advantage is it easily slides on over fuzzy shirt or sweater sleeves (wool or fleece), but can chill your nekkid arms when you first pull it on over a short sleeve shirt. The exterior fabric has a cozy fleece facing, as if the goal is to warm the outside air. But I value the two top pockets for commuting, iPhone etc., the longer length for covering untucked shirts, and all else is good.