Fluval blue fine filter pads are uniquely designed to fit Fluval canister filters. These blue polyester pads capture small particles and help maintain crystal clear water. Use the blue fine filter pads after using Fluval fine filter fleece pads (water polishing pads) to maintain water clarity.Fluval Fine Filter Foam FX Series+ captures small particles and debris+ helps maintain clear water+ for freshwater and marine water enviroments+ rinse frequently and replace every 3-4 months+ for Fluval External Filters FX4/5/6+ Package content: 3 pieces+ Fluval No. A248