Pentek FloPlus-20BB - 20" x 4.5" Big Blue Carbon Block - Cyst 0.5 Micron FilterThe Pentek FloPlus 20BB is a 20" x 4. 5" carbon block filter cartridge engineered to reduce sediment, chlorine taste and odor, and protozoan cysts down to 0. 5 micron with 99. 95% cyst reduction efficiency. With a 50,000 gallon chlorine reduction capacity at 4 gpm and NSF ANSI 53 certification, this Big Blue cartridge delivers whole house filtration performance with the dirt holding capacity of a 10 micron filter. SPECIFICATIONS Core Performance Data