These are high precision servo which gives you an amazing torque of 13 Kgs which is great for your 50 cc planes or less.

FEATURE:
● High performance  digital  standard servo
● High-precision Taiwan-made aluminium gears with hard anodizing
● CNC aluminium middle Shell
● Dual ball bearings

SPECIFICATIONS: 
● Dead band: 2μs    
● Working frequence: 1520μs / 330hz
● Motor: high quality core motor
● Operating Speed (4.8V): 0.20sec/60° 
● Operating Speed (6V): 0.18 sec/60°
● Stall Torque (4.8V): 11.75kg.cm (163.21oz/in)
● Stall Torque (6V):  13.06 kg-cm (181.40 oz/in)
● Dimensions: 40.5X20.2X38mm/1.59X0.80X1.49in
● Weight: 62g (2.18oz)
● Connector Wire Length: JR  265 mm (10.43in)
● Bearing: 2BB