Pack of 3x 5-micron Silver Impregnated Carbon Block Filters Activated carbon is a form of carbon that has been treated with oxygen to make it very porous, allowing for a larger surface area for chemical reactions to occur. The carbon absorbs organic materials and Chlorine from the water it comes into contact with. The Impregnanted Silver in the Cartridge is helps to kill bacteria, inhibiting their growth on the carbon filter and extending the life span of the cartridge. The Silver Nano Activated Carbon Block is enclosed in a 5-micron filter to catch tiny carbon dust particles that may break off during the filtration. What's in the box 3x 10 inch slimline (10x2.5" size) Silver-infused Carbon Block Filters