This is the Futaba S3156 Micro Digital Metal Gear Servo.FEATURES: For small electric powered aircraft modelsINCLUDES: Futaba S3156 servo, 0.79" (20mm) long 4-point horn, 1.6" (40mm) long 4-point horn, 0.79" (20mm) diameter round horn, four 2x11mm mounting screwsSPECS: Torque: 28 oz-in (2.0 kg-cm) @ 4.8V 33 oz-in (2.4 kg-cm) @ 6V Speed: .13 @ 4.8V .11 @ 6V Size: 0.9 x 0.4 x 0.9" (22 x 11 x 22mm) Weight: .32 oz (9.3g) COMMENTS: Do not use this servo with gas powered models or models requiring high torque Do not exceed 6V supply voltage or apply high load to servo. Do not use standard size servo horns. Use horns designed only for micro servos. For replacement horns use part numbers FUTM2005, they fit very tight but they will work.