The Adventurer Opti UV water purifier is essential gear for thousands of adventurers and features a patent-pending technology - an optical eye senses water to ensure safe use and effective treatments. The revolutionary optical water sensor doubles as an integrated LED flashlight for added convenience on the trail or around the campsite: hold down the activation button for three seconds to illuminate the darkness. With a rugged design and construction trusted by thousands of endurance athletes, the Adventurer Opti is powered by two CR123 batteries making it a lightweight water purification system and keeping it operating effectively in even cold environments. The long-lasting UV lamp provides purifies up to 8,000 liters! Works in containers with a minimum 1.75 inch diameter opening. (Like Nalgene wide-mouth bottles one liter bottles.) Features: - Uses UV light to purify water - Weight: 4oz - Battery type: 2 CR123 (included) - Approx. number of liters per set of batteries: 50 - Lamp life: 8000 activations - Volume options: 1 click = 0.5 liter, 2 clicks = 1 liter - Effective against microorganisms - Suitable for small groups up to 3 people - Suitable for cloudy water - For daily or very frequent use - Lightweight and portable for on-the-go adventures