Paramount manufactures the Active Drains, which are unique: MDX, MDX2, MDXR3.
It is about the active drains, which do have a role in cleaning the debris from the pools spa or fountains.

The Active Drains meet all the regulations and safety rules. These drains are only very effective because they remove the debris from inside the pool. They are manufactured and supplied in eight different colors in order to better match the finishing of any pool. These drains are to be installed only in Concrete Pools, Liner Pools and Prefabricated/One Piece Pools.

They are installed in conjunction with the Automatic In-Floor Cleaning System. They are also part of the Smart Filtering System which provides big savings in water, energy and chemicals.

More details on the "MDX" page.