A double layer band and special interlock knit separate this headpiece from the crowd. Perfect for warmer days or high aerobic activities.. . 100% Merino Wool. Merino 250: Smartwool's heavier base layer fabric for more insulation in cool to cold weather. Double-layer Interlock knit construction. Clean finish seams for bulk-free fit. Reversible design for variety. Machine wash cold. Knit in Vietnam.