The Camelbak All Clear Pre-Filter is designed to be used for the All Clear™ Microbiological UV Water Purifier to strain out larger sediment particles prior to purification. The All Clear Pre-Filter removes particulates from water prior to UV treatment. Ideal for water filled from streams and lakes. Fits over bottle threads to protect them from untreated water. Fits most 63 mm openings for fast and easy filtering of particulates.