Zanyzap Replacement Reptology Internal Filter 45 Bio-Sponge Foam (12 Filters) Helps to optimize colonization of beneficial aerobic bacteria Assists in the removal of ammonia and nitrites Made to fit Reptology Internal Filter 45 Also fits Penn-Plax Cascade 170, Hagen Elite Internal Filter, SpongeBob Aquarium Kit Internal Filter -SBK2F/UK, Dora Aquarium Kit Internal Filter - DRAT1F/UK, WWA4 / WWA5 / WWA6 UK Internal Filters