ECWCS Gen III Mid-Weight Underwear Top (Level II)ECWCS Gen III Mid Weight Underwear Top (Level II) is the perfect base layer for extreme cold weather. Part of the Extended Cold Weather Clothing System (ECWCS), the cold weather top is designed to keep active duty personnel warm and comfortable all day. Made from a breathable, moisture wicking grid fleece material that ideal for layering, so it won't get too hot or impede your movement. The zip collar allows the undershirt to be worn as a turtle neck