The smallest, lightest SteriPEN®, the AdventurerOpti Water Purifier uses a revolutionary optical eye to sense the water. The patent-pending technology provides safe use and the standard insulating sleeve around the UV lamp allows purification in even the coldest of waters. Fast, light, easy and effective, the AdventurerOpti provides the ultimate protection from waterborne illnesses. Giardia, cryptosporidium, bacteria and viruses are all destroyed in seconds-by SteriPEN® UV light. The UV lamp provides up to 8,000 one-liter treatments. UV purification works as the ultraviolet energy emitted by the light is absorbed by the cells of the microbe, preventing cell enzymes from 'reading' its DNA. Without intact DNA, microbes can't reproduce to make you sick. The process is simple but effective, destroying over 99.9 percent of harmful microorganisms. Great for camping, hiking and backpacking.Easy to use 1 button operation; LED light quickly indicates when ready to purify, then place the pen like lamp in clear water and stir until indicator light turns green..Dirty water should be pre filtered until clear prior to treatment..The UV lamp provides up to 8,000 one liter treatments..Device works with containers with minimum 1.75 in. diameter opening (ie Nalgene wide-mouth bottles)..Low power indicator lets you know when batteries need replacing..Automatic shut off when treatment is complete..Includes black neoprene case with belt loop and 2 non-rechargeable CR123 batteries and instructions..Size: 15.5cm. (6.1in.) x 3.3cm. (1.5in.) x 2.2cm. (1.0in.).Weight: 103g/3.6 oz. with batteries.