The Berlin X2 is the latest evolution of the popular Berlin range of skimmers, used by thousands of satisfied aquarists around the world since 1993. The X2 offers a 50% increase in skimming performance over the old model, while preserving its predecessor's small footprint and compact dimensions. Red Sea's patented Triple-Pass maximizes the water-air contact time inside the skimmer's reaction chamber, stripping the aquarium water of even the smallest traces of organic pollutants, while minimizing the external dimensions and footprint of the skimmer. By forcing the water-air mixture along a circuitous route, the Berlin X2 achieves a total surface area equal to that of much larger conventional skimmers. The X2 skimmer includes the new FoamView collection cup. It features a patented window built into the side of the collection cup, allowing for accurate, real-time evaluation of foam production. Designed for both in-sump and hang-on use, all Berlin X2 models also include a hang-on kit, enabling the in-sump configuration to be converted quickly and easily for hang-on aquarium setups.

(information taken directly from the manufacture's website)