I sincerely hope you have the Avis part number for the sand filters correct....
we don't want any mistakes and you have confused that with the cupola smoke launchers... after all, those wipers under hard work are.. likely to smoke abit.
I read the specs on the Beaver model, to be honest, i've had prior experience of this specification on similar models.
When it refused to be co-operative all i came away with was " Dam, Dam, Dam "