However you want to wear it - under a wetsuit, under Lavacore full suit, stand alone or paired with Lavacore shorts - this extremely versatile vest covers your core organs from the elements - at an affordable price. Flexible, durable and water repellant/resistant outer layer Windproof and breathable middle layer Warm, moisture-wicking, inner fleece layer Extended material on back to keep vest from riding up Lightweight and 4-way stretch Lavacore is neutrally buoyant All seams are overlapped during flatlock sewing UPF 50+ protection Sizing: XS, SM, MD, ML, LG, XL, 2XL, 3XL, 4XL