Fresh hollow fiber filter cartridge for the DayCap In-Bottle Filter. Proven Filtration: Hollow fiber filtration media is the same technology as our most popular and field-proven filters and filters up to 1L/m. Safe & Effective: Each filter is individually tested to ensure it meets all EPA & NSF guidelines for the removal of 99. 9999% of bacteria and 99. 9% of protozoa.*Easy Cleaning: Simply shake to clean with it attached to your bottle to break up particulates and restore flow rates. This replacement filter cartridge is the same high-flow and effective hollow fiber filter that came with your original DayCap In-Bottle Filter. Right out of the box it's ready to twist into place and deliver fast, safe, and easy access to clean drinking water.