I have a x3 sabre from hongnor,the steering servos started jittering,I need help on choosing the right servos according to availability in the Indian market.

Steering servos must be strong 15kgcm min is good and it should be fast so that it'll respond fast. High torque and high speed servo consume more current, better choose 7.4V version if your Rx can tolerate that voltage and the throttle servo can also tolerate. If you're planning to race, then go for premium brands like Savox.

and always go for metal gear .and you can check few servos here if you need . www.hobbysea.com

Personally, I'd go for the Hitec one. I used to have that servo in my E-Maxx but then I put it in my Stampede and got this servo instead. I am loving it. Costs a little more than the HS-645, but it's digital AND it's dustproff and waterproof.