These are little plugs that stops water and dust entering your O2 feed hose, scrubber head when you remove the scrubber or the hose from your inspiration or evolution
They also fit the ADV and it's HOSEAS WELL AS ANY STANDARD SECOND STAGE REG like on the kiss rebreather
Once you remove the scrubber you just screw in these DELRIN plugs to your feed hose and then the other on to the scrubber head (THIS ONE HAS A SEAL INSIDE THE CAP,NOT SHOWN IN THE PICTURE)
Then you can hose down or immerse your re-breather in fresh water.
Or fit them to stop salt spray getting in when changing the stack on a boat, with out the worry of getting water and dirt in the wrong place.