AVCS System: Since the rudder trim changes (caused by wind and other meteorological changes); the front, rear, and other heli attitudes change and are automatically canceled; tail (rudder) operation is easy, making it perfect for 3D flight. (ALSO KNOWN AS HEADING HOLD GYRO) Specifications: Model NO: GM 700 Weight:14.7g /.52 oz(include wire and connectors) Dimensions:28 x 28 x 20mm Operating voltage:+4 to +6V DC