THE YANKEE FLIPPER is the definitive squirrel proof bird feeder. Birds love to eat from it, but grey squirrels are prevented from eating from it in a way that will make you smile. The weight activated feeding perch is calibrated to react to a squirrel's weight. When a squirrel steps on the perch, a connection is made with a motor that makes the perch spin, and the squirrel is flipped off the feeder. Thus, the name YANKEE FLIPPER. The unit comes equipped with rechargeable nicad batteries and a battery charger. Would you expect anything less of Droll Yankees? 21' long, 4 ports, 4 qt. cap., 2/ctn., 10 lbs.