Duofold Thermals Mid-Weight Youth Ankle Length Bottom # 623D base-layer-underwear closure Mid-weight jersey fabric feels great against youngsters skin. (Its cotton-rich for softness, with enough polyester to withstand tough wear &amp; tear.) Two-ply design traps body warmth to create a thermal barrier. Ribbed cuffs provide cozy fit. Flat-lock seams wont chafe or dig. Tag-free elastic waistband wicks moisture for quick-dry comfort. 60% cotton/40% polyester bi-ply jersey. Same as 623B