I believe the fitting is standard but have seen some comments that the flow rate is high as trucks takes loads ot it.
Been keeping an eye on this as we have new VW with Ad Blue. An issue with our car is the filler is buried in the boot floor and I really wouldn't the stuff to go spurting out! And it would be a pain in filling station to have to remove the spare etc.
I've bought the filler tube and a 5L bottle of Ad Blue from TPS (VW's trade parts place). They had 5, 10 & 20L containers. I think MB sells the tube too and it may well be the same. VW one was only about £6.