20″ x 4.5″ Gravity Flow carbon impregnated Sediment Cartridge. 10 Micron. These cartridges are designed to give some carbon taste, odour, and colour removal while on gravity feed or very low pressure They are made from very fine carbon dust impregnated into the Poly Spun material. The Micron rating on these is approx. 10 Micron. These are not to be mistaken for full Low Pressure Drop Carbon Cartridge. These are primarily a sediment cartridge with carbon impregnation for taste and odour advantages.