[Compatible with for Tetra Whisper filter] The size of filter cartridge 5.1 in L x 6.7 in W. It is match perfect for large tetra whisper bio-bag external filter PF20, PF30, PF40, PF60, for whisper external filter IQ20, IQ30, IQ45, IQ60, for whisper 20i & 40i internal filter. Good idea for Tetra Fauna ReptoFilter 50 gallons (125 GPH). [Superior Filtration Performance] Made of dense double-sided superior cotton and super activated carbon, it provides triple water filtration that removes 99% of filter debris and fish waste, keeping the water clean and healthy and promoting healthy fish growth. [Replace Filter Cartridge Regularly] To ensure optimal cleanliness, we recommend replacing the aquarium filter cartridges every 2 to 4 weeks for your fish tank.It contains 12 pack aquarium filter cottons. Colour:As Shown Material:Composite Materials Package Contents: 12 * Large Filter Cartridge Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.