Interpet Filter Hide Castle is designed to hide the aquarium equipment in the back corner of the aquarium. Using the suckers on the back they can be firmly pressed against the back corner of your aquarium effectively hiding your filter without obstruction. Once in place the illusion of an uncluttered underwater world is complete. Designed to take Interpet PF and most other makes of Internal Power Filter. Each piece comes complete with 4 replaceable suckers.