Perfecto undergravel filters are manufactured with a unique design that allows uniform flow across the entire tank. Heavy duty injection-molded plastic holds up under the heaviest rocks and tank d‚cor. UGF filters are easy-to-install and include fish protectors on the flow spouts and raised tube connectors to keep gravel from falling beneath the plates. Ideal for use with air pumps, power heads, and refillable carbon cartridges. Made to fit 20 Long or 29 gallon Tank.