The Steripen Pre-Filter is the perfect companion to your Steripen water purifier, ensuring clean and safe drinking water wherever you go. Made specifically to fit Nalgene wide mouth water bottles, this pre-filter removes debris and particles from your water before it goes through the purifying process. This helps to prolong the life of your purifier and ensures that you have pure, delicious drinking water every time. Easy to use and clean, the Steripen Pre-Filter is a must-have accessory for outdoor enthusiasts, travelers, and emergency preparedness kits. Stay hydrated and healthy with the Steripen Pre-Filter.