The Aircraft Magneto Timing Light Model E50 is the industry standard. Designed specifically for the internal timing and synchronization of aircraft magnetos, the E50 safely absorbs the current from the magneto's impulse coupling -- so there is no danger of engine firing while adjustments are being made.
The E50 timing light takes all the guess work out of the magneto timing process. And it's quick and easy to use: simply attach the three clips to the magnetos and adjust them until the E50's two blinking lights are synchronized and the buzzer changes in pitch. That's all there is to it. Perfect timing.