The Flanders Warm LS Base Layer with Neck Warmer is the warmest base layer Castelli produces in their winter range. The entire body of the Flanders Warm LS is constructed from SottoZero multi-denier 100% polyester fleece fabric. This multi-denier poly fabric has a 3D structure and a rib-knit profile. This simply means the fabric has a multiple density construction which creates a 3D structure that elevates the fabric off of the skin for greatly improved wicking and moisture management. Rib-knit is the corduroy looking profile on the exterior of the garment that promotes air flow between the base layer and outer shell. Castelli combines multi-denier 3D fabric with a rib-knit profile for complete success with wicking and moisture management.

The Flanders Warm comes in black, as well as a soft grey color to help retain heat during colder days. The finish of the base layer is smooth to the touch and very comfortable on the skin. Other details include a 4-needle flat-lock stitching that lies perfectly flat and will not bind. A built in neck warmer keeps you warm and unfurls to an entire chin warmer for when the temps drop.