#FC2 - Multi-Pore & Undertow "E" and Clear-Free Premium Undergravel Filters (2/pkg.)  $2.99

#FC3 - Universal - fits ALL Undergravel Filters (2/pkg.)  $3.99

#FC4 - Fits Undertow and Perfect-A-Flow (2/pkg.)  $2.99

#FC5 - Use in any Power Filter (2/pkg.)  $3.99

#FC5H - Holder w/aerating FC5 cartridge (1/pkg.)  $3.99