The filter is for a Donaldson body which i believe is being used on current military units for work in dusty/sandy areas. the body is designed so a secondary filter can be used inside the primary cartridge .
Answer found as advised from Filtration ltd, ( although not cheap! see below ), also other option is a filter made by FRAM .
Thank you for your enquiry. Im pleased to confirm our price and availability for the part number provided.
P78-3498 - £33.83 each, 4 week lead.
Delivery will cost £10.00. Prices are exclusive of VAT.
If you have any further questions please dont hesitate to contact me.
Kind regards,
Nathan
Filtration Ltd
303B Dean Road
Avonmouth
Bristol, BS11 8AT