Castelli used Forcefield Fabric to construct the Velo Vest. This extremely lightweight fabric is a 30 gram, ripstop material that is windproof and water-resistant. It was given a DWR (Durable Water Resistant) coating. It's so light, in fact, that you'll barely notice you're wearing it. Additionally, it is highly breathable so that when you are working up a sweat you won't get drenched from the inside-out. Furthermore, the vest features mesh side panels to help heat ventilate from your core. It should be noted that while the Velo vest is ideal for drizzle or windy conditions, it is not constructed with fully taped, waterproof seams. If you need a layer to keep a deluge at bay take a look at the Castelli Pocket Liner Jacket
The vest was cut with a longer back for better coverage. A high mesh collar keeps drizzle from running down your neck, and when the sun comes out, the mesh neck turns into a pocket in which to store the entire vest. It only takes up half a jersey pocket so it's perfect to carry on those days when the sun doesn't look like it's going to keep the rain at bay. Castelli added a reflective logo and back tabs to increase your visibility in low-light conditions.
Material: ForceField micro ripstop, DWR coating, [side panels] mesh
Fit: form fit
Venting: mesh side panels