WIX, WIX, WIX did I mention WIX. they are built really good and are the same as my aircraft filters but way less expensive. I know I cut them both open with a filter cutter to see what is going on in the motor. In Canada I buy them for $6-7. If you fellow US listers get together and group buy ........ well I buy Fleetguard filters for my Cummins 10 at a time for $2.69 ea.