Pentek - CFB-PLUS20BB - 20" x 4.5" Fibredyne Modified Carbon Block Filter - 5 MicronPentek Fibredyne Technology CFB PLUS20BB 20" x 4. 5" Modified Carbon Block Filter 5 micron dual action filtration that combines sediment reduction with enhanced chlorine removal in a single cartridge NSF ANSI 42 Certified Materials 5 Micron Rating Fibredyne Technology FDA Compliant Materials The Pentek CFB PLUS20BB represents an evolution in carbon block design, using proprietary Fibredyne technology to bond powdered activated carbon directly onto a