*Drilite® is Mountain Equipment's own breathable waterproof fabric. They say, "Drilite® is constructed from a hydrophilic, Monolithic Polyurethane Membrane that is both waterproof, breathable and durable. A monolithic membrane provides all the protection you need yet measures a minuscule fifteen microns thick. It allows us to make jackets light enough for fell runners, packable enough for alpine hikers and tough enough for serious mountain routes. Waterproof: Drilite® has a 20,000mm hydrostatic head to keep you dry. A benchmark minimum standard of waterproof performance necessary for all-day, all-weather protection. Breathable: Drilite® uses a Polyurethane Membrane to offer a high level of breathability (20,000g/sqm/24h) and ensure you stay comfortable, even when working hard in the mountains. Durable: Drilite® fabrics have been carefully developed to be both durably waterproof and windproof whilst offering performance characteristics (such as weight and stretch) that are specific to end-use. Monolithic Membrane Technology: Using a pore-free construction that is highly breathable, the Monolithic Membrane actively transports water vapour through its molecular structure whilst at the same time forming an impenetrable barrier to water and dirt from the outside. Formed from a single solid-state layer, just 13 to 15 microns in thickness, this clear and elastic membrane is then laminated to a number of outer face-fabrics, each chosen for particular performance characteristics. On the inside a pigment print is then applied, combined with a permanent Silica coating to aid moisture absorption and create its dry-touch feel."