Destroy harmful waterborne bacteria in your water with the Hydro-Photon SteriPEN Adventurer Opti. The SteriPEN uses UV light to kill giardia, cryptosporidium, bacteria, and viruses in just a few seconds, so you can stay hydrated on the trail without having to worry about getting sick. And at a scant 3. 6 ounces and 6 inches long, the Adventurer Opti won't weigh you down or use up a ton of valuable pack space.