This device tricks the computer into thinking the engine is running rich therefore cutting back on fuel. It attaches to the wire on the o2 sensor that sends the fuel mixture signal back to the computer.
It works great with an acetone mixture usually giving gains of 5%-10% in fuel economy. It's in like new condition and comes with all installation instructions. Fairly simple to install. You will probably need some more wire and a voltmeter to properly tune to your engine. Every engine has a different sweet spot for the best fuel economy.
Retails for $90 selling for $60. Any questions feel free to shoot me a line.