The rating that is used on the Eurohunter Series that being 5000 or 3000 will determine the level waterproof/breathable performance. If you take an area of fabric the size of a rain droplet and imagine a rain droplet that is 5000mm tall on that area. The rug will withstand this level of water pressure therefor giving you a 5000 rating. On the other side of this is the breathability of the rug. The Aquabreathe technology rating is a measurment of how much water vapor or sweat to pass out through a square meter of fabric in 24hrs. With a rating of 5000 it will allow for 5000gm of water vapour to pass through the surface.