The YANKEE FLIPPER is the definitive squirrel proof bird feeder. Birds love to eat from it, but 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 recharger. Would you expect anything less of Droll Yankees? 21" long, 4 ports, 4 qt. capacity. #YF.