JR S3415 Servo. XBus. 
Specifications:
@ 6.6v 3.8kg-cm 0.11 sec/60deg
@7.4v 4.3kg-cm 0.10sec/60deg
@8.4v 4.9kg-cm 0.09 sec/60deg
Weight: 30 grams 
Dimensions: 26.5mm x 15.0mm x 33.0mm