STERIPEN CLASSIC SAFE WATER SYSTEM Battery powered (UV) water purifier. System pack includes Pre-Filter, water bottle and Classic carrying case. Pre-Filter stores on water bottle. Purify a half-liter in 48 seconds or a liter in 90 seconds. Easy operation: activate, place lamp in water and stir. Shuts off when finished. Destroys over 99.9% of harmful bacteria, viruses and protozoa, like Giardia and Cryptosporidium. Certified by the Water Quality Association. Fast, safe, effective and chemical-free. Doesn't alter taste, pH, or other water properties. Reusable to purify up to 8,000 liters. Purifies 100 liters on one set of lithium batteries. Requires 4 AA batteries (not included)