Three 5 Micron Polypropylene String Wound Water Filter Cartridges Compatible with 3M Aqua-Pure AP814 & Pentek WP5BB97P, WPX5BB97P, WP5BB975 by CFS FREE SHIPPING. Three 5 micron 4.5 X 10 inch string wound water filter cartridges Compatible in all large diameter and "Big Blue" style water filters Made in the USA. High quality - low cost! 20 gallon per minute flow rate Replace cartridge every 6 months or upon substantial pressure reduction