The TetraTec In800 Plus Internal filters is a total redesign of the old Tetra internal filters with great new features and benefits. There are 4 sizes in the range to meet most requirements. All filters have twin foams for easier maintenance and have an easy to use flow adjuster. The main body of the filter remains in place while filter sponges or impellor are cleaned. All filters have an adjustable air venturi system to deliver additional oxygen to the aquarium. Filters come with a 2 year guarantee.