HQRP 10-Pack Pre-Filter Foam for Tetra Pond FK3 / FK-3/26594 Filtration Fountain Kit, 19016 Replacement Coaster HQRP&reg; 10-pack Foam Pre-filter Replacement + HQRP&reg; Coaster; Foam filter for removing debris and prevention pump from clogging; The foam insert is used in pre-filter of FK3 Filtration Fountain Kit; Measures 3-3/4-inch length by 2-5/8-inch diameter, 1-inch diameter hole in center that goes all the way through; 100% Compatible with Original filter. 2 weeks DOA replacement warranty!