The Fluval A276 is the correct replacement filter for the following:
The Fluval A276 BioLife Filter For Mech 3 - 10-Pack is a ten pack of replacement duo-density cartridges for the Fluval Mech 3. This Mech 3 replacement features an outer worn polyester pad that removes fine particles. This replacement aquarium filter also features UltraGrade carbon granules that absorb liquefied wastes (gaseous impurities), medications, and dyes.
Fluval A276 BioLife Filter For Mech 3 - 10-Pack specifications: