Why extra (o-ring) groove on Surefires?

[cfromc]

I am looking at two of my Surefires and it appears that there is an extra o-ring groove on both ends of the bodies (M3+C3). Is this there for a purpose or is there actually supposed to be 2 o-rings on both ends? If I put the 2nd o-rings in will it be better or cause problems? Both of the SFs I'm looking at were "nearly" new but not 100% NIB so I don't know how they came from the factory.

 

[highorder]

I add extra O rings. I use clickie switches almost exclusively, so there is no downside.

 

[tebore]

Well the models that have Seal/Diving counter parts usually just have extra o-rings and beefed up parts. No surprise that some of the bodies would have extra grooves.

 

[Patriot]

My M3 and M2 have two orings.....It won't hurt anything if you put the other o-ring on if you want to.

 

[cfromc]

Thanks guys. For 20 cents, I'll put extra ones on.

 

[BBL]

The twist switches are considerable harder to operate - thats the only downside.

 

[GeoffChan]

i think its for extra water proofness.

Geoff

 

[Size15's]

The Millennium Series comes standard with two o-rings on the TailCap-end of the bodies.
The main purpose of an additional o-ring seal is to allow for the component to be rotated underwater - the 2nd o-ring helps to ensure the seal remains watertight.
Secondary purpose is to help prevent accidental rotation of the component; in storage, transportation, carry & use.

Al