The Skilter 400 is the largest Skilter offered. It is ideal as a primary filter for aquariums up from 30 to 100 gallons and can be used as a supplemental filter on larger aquariums. The protein skimmer is effective for aquariums up to 125 gallons. The larger, powerful motor is rated for a flow of up to 400 gallons per hour. The Skilter 400 is packed with two dual-media Bio-Matrix cartridges. Made in the USA.