ColdPruf Men's Dual Layer Long Sleeve Union Suit Two-layer engineering with Merino Wool, traps body heat between layers, resulting in chill-blocking warmth Full button front with horn style, branded buttons Single button vertical rear drop Tagless labeling for extra comfort Fits loose on the body, generous cut for full range of motion. For best fit wash before wearing Best for dressing with minimal layers in very cold to extreme cold weather and low to medium activity