Trusted on mountains and trails for over 15 years, SteriPEN® Classic is the best-selling portable UV purifier of all time. Since 1999, hundreds of thousands of people have ensured their drinking water is safe and avoided ruined adventures with SteriPEN® Classic. The next generation of Classic operates on four AA batteries batteries. With one set of alkaline batteries, Classic 3 purifies up to 50 liters or supercharge your Classic 3 with lithium batteries and treat up to 150 liters. With a lamp life of up to 8,000 liters, you’ll be drinking safe water for over 7 years!