The bulb upgrade is actually a "end of light unit" upgrade.
The entire end of the weapon light is removed and replaced with a new one that contains the LED bulb, reflector, lens, and so forth.
Help me understand...
Is the upgrade you are talking about different from the factory LED lights available from SureFire?
Does one buy the factory LED light (617LF LED or 617LFG LED) and send it off to another company for the upgrade?