The Castelli Women’s Flanders 2 Warm Long Sleeve Baselayer. This product was made for the conditions of Flanders in February. Or basically any month in Flanders 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. SottoZero Fleece multi-denier 100 polyester fabric. Flat-lock stitching. Mesh armpit insert. Flat hem tucks away in tights. -4deg-10degC 25deg-50degF. Weight 103 g.