It is waterproof and windproof and breathable enough to dissipate perspiration even when hiking in the spring rain of the Smoky Mountains. Appropriately layered, one can stay relatively dry inside and out in any earthly environment when wearing this other-worldly beauty of a shell. Fabric: Patagonia's proprietary H2No waterproof/breathable and similar stretch fabric. Fill: None. A human body, perhaps. Price Paid: $225