Katadyn Micropur Classic MC 2500. Natural silver crystals will treat 10,000 liters or 2,500 gallons of water. Will preserve water from 6 months to several years- depending on the way it's stored. Water can be re-treated repeatedly. Katadyn Micropur keeps water in tanks and containers free from bacterial contamination, water stays fresh and potable for extended periods. Katadyn Micropur is based on silver (bacteriostatic action). It is neutral to the taste and simple and safe to use. Ideal for Boats, RV's, Campgrounds, Etc. Weight: 3.5 oz or 100g. Note* One measuring spoonfull will treat 25 gallons ~ 100 liters of water. Spoon comes with the package.