The Castelli Unlimited Puffy Vest is great on the bike, back packing or anytime you need a little extra warmth when you are working on fitness in cooler weather. The Castelli Unlimited Puffy has amazing warmth in a lightweight, compact vest. The microfiber shell keeps wind out, while the Polartec Alpha Direct insulates body heat with very little extra weight. Air circulates through the side panels; sweat evaporates and your skin can breathe as you push your body hopping a mountain bike over obstacles, ascending a mountain road on your road bike, or hiking through brush in cool fall weather. The stretchy side panels create an athletic fit so no vest will snag on limbs on an off-road trail or flap in the wind as you descend a mountain road. The stretch also helps keep the 2 large rear pockets in place even when they are loaded with energizing food. The stretch side panels as well as the rest of the vest are treated to be water repellent so any light rain or road spray will role off. When you need extra ventilation, the YKK Vislon zipper with U-shaped zipper pull is easy to open. The Castelli Unlimited Puffy Vest can be used in a wide range of conditions. Fall or Spring, sun or drizzle, bike ride or hike, the vest can be packed into rear jersey pocket or backpack for outdoor adventures in mildly cool weather.