Hydronix - SMCB-4520 - NSF Carbon Block Filter 4.5" x 20", 0.5mHydronix Professional Series SMCB 4520 NSF Certified Carbon Block Filter Industrial grade 4. 5" x 20" carbon block filtration at 0. 5 micron for whole house, commercial, and well water applications NSF Certified 0. 5 Micron 20" Length WHY IT WORKS High capacity carbon block filtration for demanding applications Solid Carbon Block Compressed activated carbon removes chlorine, taste, odor, and organic contaminants through depth filtration with