Paintball

[chopper duke]

Not terribly uncommon on mags. PS has it with the liquid.

I've got an extra if you want it.

I was hoping it was a new part we could all take turns at making up names for. If that's the case, I call it the Nancy Reagen since there's only one of them.

[Robertsr]

All they ever did for me was restrict the flow and make my mags chuff. I have a little box full of them somewhere...

[Pif]

I recognized the filter material, and could only hypothesize. Neat little item

[Hollywood]

It is a version of the Howdy Filter Jim "Howdy" Mcguffog of ASO(Action Sports Outfitters) installed the first ones on very early Auto Mags(one of the very first Mags )to stop the valve from being contaminated by dirt found in CO2 ASO made a special housing that attached to the Marker that accepted a cartridge type filter which could be replaced when needed.several companies copied this idea and made changes like the example you have which would go inside the Tank.Howdy Left ASO in 1994 to work for Airgun Designs--This was one of the many mods. ASO was known for from 1988-1995