CARBON BLOCK FILTER – The Activated Carbon Block Filter is the second stage of your RO unit. It reduces chlorine by up to 99% and conditions the water prior to the RO Membrane for up to six months. REDUCES CHLORINE AND CONDITIONS WATER – The carbon cartridge boosts water quality. It installs in seconds. Use with AquaticLife Twist-In 3-stage RO and 4-stage RO/DI units. Size: 2.75" x 11". SIMPLE TWIST-IN DESIGN – The Twist-In Carbon Filter cartridge is designed to simply twist into the pivoting head on the Aquatic Life 75 and 100 GPD Models of the Twist-In RO and RO/DI units. TRIPLE-SEALED FOR DURABILITY – The high-quality materials used in this reverse osmosis replacement filter ensure durability. It’s three o-rings ensure a tight seal for trouble-free operation. UNSURPASSED QUALITY AND SATISFACTION – AquaticLife manufactures an assortment of aquarium and water filtration equipment. Every product that goes out the door meets our highest quality and standards.