Penn Plax Cascade Pro Carb Canister Filter for Aquariums, 8 Total Filters (4 packs with 2 filters in each pack) 8 Total Filters (4 packs with 2 filters in each pack) Filter media fully enclosed in a disposable nylon-mesh bag. Convenient, ready-to-use filter bags for use with your Cascade cannister filter. Contains Pro-Carb laboratory quality activated carbon.