You'll have to be a little more specific. Don't take this the wrong way, it's meant as friendly forum advise, but asking a question like that without giving out any other information regarding your chosen application just makes one look a complete berk.
What are you doing with them? (ie, bashing or racing)
What car?
What motor/esc combo?
If you want help, then people need to know details about your problem. Little life lesson for you. You can have that one for free.
