W
Welder
Sorry seems to be irrelevant now!
I don’t know the official spec, but have used them on tank fed (0.2bar) when the black ones were sluggish and they then worked a treat. This is on a new installation so the black washer was new too.
However a quick google to try and find spec and they seem to have disappeared?!
I have one left and none of you can have it!
Sorry is NEVER irrelevant pal; not ever. 😉