Size A fits Marineland Penguin 75,100 and penguin pro 100 also fits Aquatech 5-15 power filters
Size B fits Marineland penguin 150, Penguin pro 125,175 also fits Aquatech 10-20 power filters
size c fits penguin 200,350 penguin pro 275,375
Size E Fits Emperor 400 and Emperor Pro 450
Size Z fits Contour 3 and 5, Portrait Aquarium, Silhouette,Eclipse system 2,3,Hex5, Corner 5 and hex 7