20" Big Blue Carbon Filters from Big Brand are manufactured using high grade hand selected carbons for each specialilzed appliation. Coconut shell has a small pore structure and has a high capacity for chlorine reduction and VOC reduction. Coal based carbon is excellent for taste, odor, and color reduction caused by naturally occuring decaying plant and animal matter. Our proprietary chloramine reduction carbon is specially engineered to reduce chloramines that pass through ordinary commercially available carbon block and granular activated carbon filter cartridges.