This is the HS-503HD Ultra Nano Digital Aircraft Servo from Hitec.

FEATURES: Metal Karbonite gear train
          Ideal for micro 3D, sport aircraft and small helicopters
          Fully programmable digital circuit
          Three pole motor

INCLUDES: HS-35HD Ultra Nano Servo with two 1.1" (28mm) double arms, one 2.1"
            (54mm) double arm, one 1.2" (31mm) double arm, one 0.67" (17mm)
            four point arm and three mounting screws

REQUIRES: Installing in aircraft and connecting linkages

SPECS:    Operating Speed: 0.10 sec @60°
          Output Torque: 11oz.in (0.8kg.cm)
          Weight: 0.16oz (4.5g)
          Size: 0.73 x 0.30 x 0.61" (18.6 x 7.6 x 15.5mm)

COMMENTS: Operating voltage should not exceed 4.8V.

                                                                   jxs 08/18/11
                                                                         ir/jxs