I had purchased a Argon/CO2 regulator for my welder off of amazon. 

The regulator came with a CGA-580 and CGA-320 valve fitting adapter.
 

When I received the order I discovered that the regulator didnt come with the required nylon washer. So I made my own and printed it in white TPU. 

100% concentric infill. 

It seems to work and seal. If this print eventually fails, ill try again in PLA.

These washers are single use, crush style washers.