If you’ve traveled, hiked, or spent any number of weeks in a developing country, chances are you have a story: hours spent crumpled on the floor of a bathroom, midnight nausea-induced runs into the woods, short-cuts through the temple tours for another few hours in a hostel bed.

There are several choices of water purification to prevent such an episode, boiling water and using purification tablets such as iodine among them. But perhaps the most efficient purification device out there is the Steri-Pen, a portable tool that uses ultraviolet light to zap viruses, bacteria and protozoa, like Giardia and Cryptosporidium. It takes just 90 seconds for the Steri-Pen’s LED UV bulb to treat one liter of water, and it leaves no aftertaste. All you have to do is place the Steri-Pen’s glass wand in a water bottle, press a button, and stir for a minute and a half or less. The battery life varies between different models of the Steri-Pen, treating between 50 and 200 liters of water per charge.

Of the eight models to choose from, the highest rated is the Adventurer Opti, which has the longest battery life. It takes its name from the optical eye the device uses to sense the water, which prevents the UV light from accidentally remaining on when it’s not in use. The long-lasting light sustains through 8,000 water purifications. This one also includes a flashlight mode, helpful for late-night walks to fill up your water bottle. It’s just another way to ensure that finding clean water will be one less complication in your story.