These Impressive servos have a great specification, performance and at these prices are pretty phenomenal. Superb for a digital metal geared servo with part alloy case. Beat that. 

Description:
Brand:JX
Item:PDI-6221MG 20KG Large Torque Digital Standard Servo
Dead band: 2μs    
Working frequence: 1520μs / 330hz
Operating Speed (4.8V): 0.18 sec/60°
Operating Speed (6V): 0.16 sec/60°
Stall Torque (4.8V): 17.25 kg.cm (239.55oz/in)
Stall Torque (6V):  20.32 kg-cm (281.89 oz/in)
Dimensions: 40.5X20.2X38mm /1.59 X0.80X49 in
Weight:  62 g (2.18oz)
Connector Wire Length: JR  265 mm (10.43in)
Bearing: 2BB
Usage:For RC Models

Features:
- High performance  digital  standard servo
- High-precision aluminium gears with hard anodizing
- CNC aluminium middle case
- Dual ball bearings

Includes 5 servo arms, grommets and sleeves