this is the replacement servo for the discontinued S9451
This is the S9452 Digital Hi-Speed.Hi-Torque Servo for many applications,
especially, On-Road Touring Car Use and Comes with "J" Connector Installed.
           This servo is designed to be used with 6V receiver packs.

SPECS: Speed: .11 sec/60° @ 6V Torque: 127.8 oz-in @ 6V (9.2 kg-cm @
6V) Weight: 1.76 oz (50g) Length: 1.57" (40mm) Width: 0.8" (20mm)
Height: 1.32" (33.6mm)

         This servo can produce high-current draw from your batteries.
         If using NiMH or LiPo batteries, make sure they are capable
                        of delivering sufficient amps.

BEST servo for trex 600 !!!ULTRA fast  hit tork  dig servo for trex 600 great for cyclic (you need 3)
buy 2 or more and Save $$$$

Just read specs these are some of the BEST rate servos  for your trex 600  they ROC

SPECS:    Length:       1.57"             (40mm)
          Width:        .78"              (20mm)
          Height:      1.45"              (37mm)
          Weight       1.83oz             (52.g)
          Operating speed:     .10 sec/60 degrees at 4.8V
          Output torque:       91.65oz (6.6Kg.cm) at 4.8V

Blowout Sale!

Sport Hi-Torque Digital Servo unreal  value digital servo reg 29.99

DS821 Sport Digital Servos

Torque: 72 oz/in @ 4.8v, 88 oz/in @ 6.0v
Speed: .19 sec/60deg @ 4.8v, .15 sec/60 deg @ 6.0v
Size: 1.50"x.94"x1.47"
Weight: 1.5 oz
Ball-Bearing: Single
Motor: Cored

SAVE $$$ With This Great Combo for T-rex and Lepton!!!! 
The 401 Gyro and Futaba digital 9650 work fantastic together considered getting a medusa 2amp 6volt BEC to optmize servo speed, also for T-rex you will need special boom mount to mount 9650: cnc boom mount, 

Futaba GY401 Gyro with SMM Technology

Futaba GY401 is a High Performance, Compact and Light Weight (AVCS) Angular Vector Control System gyro developed for model helicopters. Because the sensor and control circuit are integrated, it is simple to install.