Waterproofing Surefire

I've heard a lot of talk about adding an extra o-ring to the tail of a surefire for "waterproofing" and that seems to do the trick to make them even more (water resistant). I think I've figured out a way to help close that gap between weather resistant and waterproof by adding not one but three additional o-rings to my flashlights which include a C3, C2, 6P, and even a G2 for a total of 5 o-rings per light, as opposed to just 2 stock. I started by adding an extra o-ring to the tail and one to the head of the body just below the threads, which ironically you need a smaller o-ring for the larger head to allow the Z44 bezel to screw onto the body. The open o-ring slot is thicker than the stock slot that comes with the o-ring pre-installed.Finally the thickest o-ring goes between the tail cap and the body. Although I don't recommend swimming/diving with any surefire, but hopefully this can help some of you achieve that next level of water tightness.

Let me know if anyone needs the size/make of o-rings used, or has any additional Q's about the upgrade. -cheers

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All leaks I've noticed is never from the tailcap, or bezel. 2 main areas:
1. Glass/Plastic lens
2. Tailcap clicky

Hi fivemega, this thread isn't about waterproofing modified or custom made hosts, If read carefully it is simply about achieving a higher level of water tightness for stock (surefire) hosts. That being said the link you posted was a bit contradicting..

fivemega said:

Put a nailbender drop in into a 1x18650 body with an Electron Guru OveReady Custom switch SF head, and dropped it in a glass of water. Unit functioned until the AW 18650 3400mah battery was dead.

WaterProof

(Used an additional extra thin O ring at the head)

Nice!

Click to expand...

All in all your 3P is quite impressive, Nice work!

Sizes you used would be great!

They are all Danco o-rings. Tail: #30 7/8"O.D. x 3/4"I.D. x 1/16". Head: #40 3/4"O.D. x 5/8"I.D. x 1/16". Third ring between tail and body: #14 15/16"O.D. x 3/4"I.D. x 3/32"