The Windbloc Jacket preserves your body's precious thermal envelope without bulking you out or inhibiting your ability to move freely. To prevent wind borne chill, we sandwich a Polartec' Wind bloc laminate between midweight R2' polyester on the surface and a lighter, moisture-wicking R1 ' grid on the inside. Although the Windbloc is dry and comfortable without a shell, you can easily layer it when a storm moves in. The shoulders are seamless for pack-strap comfort; the handwarmer pockets ride high so they won't interfere with a harness. To further seal out drafts, the wind flap comes up and over the collar, cushioning your neck and chin. With chest pocket, elasticized cuffs and flat-locked seams to reduce bulk. M's R4 Jacket