Cliff Keen Weatherslayer. Long-Sleeve WeatherSlayer is designed to keep you warm and dry. Cold, wet weather never had a chance with the Cliff Keen WeatherSlayer. The lining features a revolutionary windproof, waterproof, and breathable coated Microfiber material. This highly-technical fabric is surrounded with an ultra-thin layer of polymer that repels water and resists absorption. Moisture just beads up, shakes off and dries quickly. The WeatherSlayer (tm) is the perfect foul-weather shirt to wear during those brisk fall contests or spring lacrosse games.