This is fully impermeable rain protection built from 0.51 ounce per square yard Dyneema Composite Fabric in olive tint. It has incredible warmth for it’s weight. Ventilation is done mechanically with a waterproof full zip. It’s also a full vapor barrier.
The qualities of Dyneema Composite Fabrics are well known as a super light weight and super strong shelter material. However, it also has qualities that make it an amazing clothing material. First, it is about as waterproof as it get’s. Fully impermeable. There is no question about “wetting out”. There is no water repellent treatment (DWR) that can rinse off into the environment. Water and moisture simply do not move through it. Second, because of the above quality, it is shockingly warm for little weight. Since it is a full barrier, there is absolutely no evaporative cooling and no convection. You can throw this on over a wet shirt and all the cold evaporative cooling stops. Third, due to the wrinkled and super light texture of DCF, it tends to hover off the surface of your skin or inner layer, leaving a warm air gap. Other types of rainwear will tend to stick to your skin, which negates the air gap and exposes your skin to convection from the outside.
Does it get moist inside from perspiration? Yes. I never find waterproof breathable fabrics to be very breathable and dry inside and there are many scenarios where they aren’t very waterproof from the outside either. In many situations, I’d rather be warm and a little moist from the inside with a lightweight garment than wet and cold from the outside with a much heavier garment. It should be noted that this is a garment best suited for cold and wet conditions. The zipper adds quite a bit of mechanical ventilation, but DCF is still a pretty warm layer if it’s warm out.
This item is also used as a vapor barrier liner to stop perspiration from entering your clothing during activity or sleep system at night when condensation is an issue.