The Castelli Flanders Warm Long Sleeve Baselayer was made for the conditions of Flanders in February. Or basically any month between September and May. High-loft fleece on the inside provides warmth to spare, and you\'ll love the softness on your skin with the excellent moisture management of this 100% multi-denier fabric. It\'s stretchy for a perfect fit, and the flat-lock seams add an extra touch of quality. Key Features:SottoZero Fleece Multi-denier 100% polyester fabric,Flat-lock stitching,Mesh armpit insert,Flat hem tucks away into tights,Mock turtle neck.