SteriPEN® Replacement Filter Cartridge is designed for the Water Bottle Pre-Filter and the Universal FitsAll Filter. This Filter Cartridge filters out particulates and debris using a 40X40 micron size nylon mesh filter.
Removing particulates and debris before you purify your water with SteriPEN’s UV technology is highly recommended and makes for a much more pleasurable drinking experience. If there are a lot of particulates, they may hamper the UV light from reaching all sides of the 'floaties' and some bacteria may remain and make you sick. Filtering is not required for water that is clear.