One end of this ingenious brass siphon mixer screws onto your hose bib, the other attaches to your garden hose. This fertilizer 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 16:1 ratio, as you water. A backflow preventer is integrated into the mixer. to prevent fertilzer backing up into your water supply.