Purifying water for hiking, camping, and outdoor adventures since 2001! Thousands of outdoor enthusiasts all over the world have trusted SteriPEN for outdoor use. SteriPEN’s patented UV water purification technology was first introduced to hikers and campers at REI in 2001. Easy to use – just remove the cap, activate, place the lamp in clear water, and stir. SteriPEN Outdoor models purify up to one liter of water in 90 seconds and last for 8,000 treatments.