Bought the wrong cartridges at PetSmart for my 50 gallon aquarium.  Cost me $19.00 plus tax.  I will sell for $15.00, no tax.

MARINELAND Rite Size Emperor Power Filter Cartridges provide complete mechanical and chemical aquarium filtration. These filters contain two full ounces of premium grade Black Diamond activated carbon, and remove solid waste and dirt particles with a 44 square inch surface area polyfiber pad.

Features: . Absorbs many harmful contaminants, discoloration and odors to leave water clear and sparkling clean; Patented design of the filter cartridge evenly distributes the carbon for maximum water contact with no by-pass.
Includes: 4-pack
Intended For: Emperor Filter System and the Emperor 280
Color: Blue
Size: 44 square inch surface

Instructions:
Cartridges should be changed approximately once a month.

Email me.  Thanks.  In Phillipsburg.