HQRP 2-pack Pre-Filter Foam for Tetra Pond FK3 / # 26594 Filtration Fountain Kit Coaster HQRP&reg; 2-pack Foam Pre-filters + HQRP&reg; Coaster; Foam filters for removing debris and prevention pump from clogging; The foam insert is used in pre-filter of FK3 Filtration Fountain Kit, part # 19016 Replacement; 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!