Thread adhesive/sealant?

I unscrewed the top "ring" off of my L4 in order to get rid of some dust that got in there and to straighten out the LED that went off to one side after I dropped it. Anyway, does anybody know what SureFire uses to seal the threads to keep water out and to keep the "ring" from unscrewing? Would a layer or two of teflon work as well? Thanks.

You could try some purple (low strength) or blue (medium strength) Loctite or Permatex. Other brands might not use the same color coding. Those seall pretty well, at least enough to seal the air lines in paintball guns at 800+ PSI, and they are threadlockers after all. Also some Teflon tape from your local hardware store will seal the threads, and keep them fomr coming loose.
I'd use either the Teflon tape, or the low strength Loctite. The medium might be too hard to get off if you needed to again, and I'd be afraid of having to use tools to unscrew it. You'd have to use pliers to unscrew it then. The purple might still require pliers, but ou wouldn't need so much force risking marring of the finish, especially if you wrapped the jaws in cloth or leather.