The Helly Hansen Mount Prostretch Half Zip Midlayer is manufactured with POLARTEC® 100 fabric, a lightweight, soft, knitted fleece construction that provides warmth, comfort and durability. The fabric is also designed with extra stretch, so that you can stay warm and comfortable, without feeling restricted. Flat seams reduce more bulk and provide an irritation-free fit. The inclusion of a half zip allows the wearer to determine their own levels of ventilation within the garment, creating adaptable temperature control. Internal flatlock stitching eliminates potential skin irritation and chafing, creating a highly comfortable fit that wont cause the wearer discomfort.