There's been a couple of post lately about the correct fittings to use on your SCBA. If your SCBA is a 4500# and it has the threaded male valve looking at you it'll be the CGA 347 fitting. Some of the lower pressure SCBAs like a 2216# will use the 346 fitting. The 4500# SCBA will have 3/16" to 1/4" longer threads on the valve and the female nut than the 2216's therefore the nipple on the 347 has to be longer to seal against the seat of the valve. If by chance you get a 346 female fitting the nipple won't be long enough to hit the back seat of the 347 valve and therefore not seal. Here's a photo of the two showing the longer 347 stainless fitting. Hope this helps someone along the way.
Jimmy
https://imgur.com/nLtA77E
Jimmy
https://imgur.com/nLtA77E
