One end of this ingenious brass siphon mixer screws onto your hose bib, the other attaches to your garden hose. The mixer has a small siphon tube which drops down into a bucket of liquid fertilizer (or other material) and brings the concentrate up into the hose line at a 16 to 1 ratio, as you water. A backflow preventer is integrated into the mixer. Use this mixer with hoses 50' or less in length. Needs 40 to 50 PSI of water pressure (cannot be used with drip irrigation).