Amazon.com: Big CTO Carbon Block Water Filters 4.5" x 10" Whole House Cartridges * WELL-MATCHED with CBC Series, WFHDC8001, EP and EPM Series (4 Pack) : Tools & Home Improvement
Pentek EP-20 / 155529 Compatible Water Filter - $11.46!
20 X 4.5 Inch Carbon Block Replacement Filter by Tier1 (0.5 micron)