The SteriPen Adventurer Opti is a four-inch wand that neutralizes bacteria, viruses, giardia, and cryptosporidium with UV light in seconds — no pumping, no chemical taste. An optical sensor only fires the lamp when it’s actually submerged, and the same lamp is rated for 8,000 treatments, enough for daily use over roughly twenty years. It runs on two CR123 batteries and doubles as a small flashlight.