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 fabricFlat-lock stitchingMesh armpit insertFlat hem tucks away into tightsMock turtle neck