Red Sea prism deluxe is an upgraded version of the regular prism and includes all of the unique benefits of the prism plus it incorporates two enhanced options. A surface skimmer attachment is included which is an important incorporation because roughly 70-percent of accumulated protein and waste material in an aquarium are in the top 1-inch of the water. The surface skimmer attachment allows for the top surface water to be drawn into the water inlet pipe of the skimmer, so you are constantly removing the maximum amount of waste from the aquarium. The second upgrade is the inclusion of a refillable media basket. This basket can be filled with either biological or chemical media to obtain the desired results. The basket is easily refillable and allows you to change the type of media according to your needs. Placed in the water outflow chamber the basket comes into contact with virtually all of the water as it passes out of the skimmer. The use of the media basket turns your skimmer into a full purpose filter for most marine aquariums. Measures 2-2/5-inch width.