Uneven triceps development. How to fix it?

[luckypatrick]

Here is the deal... throughout the years my triceps developed very differently from each other.
My right triceps has a really nice outer/external head, while my left one hasnt developed like this at all.

Im looking for exercises that will target the external head more so i can improve my left arm on this regard.

The tricky thing is that my left arm is actually bigger by 1/1.5 centimeters.

If anyone could provide me with suggestions on how to fix/improve this, i would be very thankful.

Cheers