The Berlin Air-Lift is a high performance, low cost internal skimmer based on the Berlin Triple-Pass principle, The Air-Lift is powered by a lime wood air-stone attached to an external air pump (not supplied), these compact units are easy to install and maintain, Rated for 240 liter / 60 gal aquariums, Dimensions: 4""Dia x 12""H, SKU: RYLHC4623