340 Pleated 25 Micron & Bio-core Filter. For freshwater and marine tanks up to 150 gallons. Includes 40 sq. ft. pleated micron cartridge and 50 sq. ft. Polystrand bio-core for biological filtration in the center core. Provides the highest usable wetted surface area for nitrifying bacteria to eliminate toxic ammonia. Consists of a drable 40 sq. ft. (3.6 m  ) filter cartridge with a core of Polystrand bio-media.