Bottle cap filter removes impurities from drinking water
Polystyrene Bottle Top Filter - Bellco Glass | Laboratory Glassware
Amazon.com: CAP FILTER Water Filtering Cap for Portable Survival & Camping Gear, Water Purifier Compatible with Water Bottle (Bottle Cap Replacement), Supply for Hiking Camping Travel Fishing (for Mineral Water) : Sports
Laboratory Filters | GVS
Amazon.com: CAP FILTER Water Filtering Cap for Portable Survival & Camping Gear, Water Purifier Compatible with Water Bottle (Bottle Cap Replacement), Supply for Hiking Camping Travel Fishing (for Mineral Water) : Sports