@mudski these Donaldson Vacuator Valves range from 25-78mm dia and the application here is for cyclonic pre filters.

The smallest (P149099 /P525956_25mm dia) looks very similar to the one in my airbox _ box is of thin wall aluminium fabricated construction and the valve is captivated by the circumferential grove shown for these two valves (Donaldson).

General info: I live on a dirt road and only ever wiped the inside of box out (installed for several yrs), never had to remove or clean the bib internal profile.