Any time you use a Castle Esc you should have a Glitch Buster cap in there, even if you are just using a S3003 std servo!

so i just need to buy glitch buster then?do you need to solder it or it connects to the receiver?

If you buy the novak one it comes with everything.

does it work as bec too or just to prevent radio glitch?

A glitchbuster is just a capacitor - just helps stop voltage dipping in rx and it glitching

thanks!i bought a rx8 instead so my worries of frying my esc ,coz i dont have bec are gone..i hope i wont need a BEC on the rx8?

You do understand that the BEC is a component built into the esc; the use of a glitch-buster capacitor or an external BEC is only required if the built-in BEC isn't man enough, or doesn't provide enough voltage for a HV servo for example. I have no issues with the MMM's built-in BEC when using a pair of 1/4 scale digital servos in my TXT-1, or a single digital servo in my GorillaMaxx; I run a glitch-buster cap on each rig as a precaution, but no issues so far..