What was the part number you were using?Cross referencing a Finnish filter manufacturers catalog I found out that the filter for Triumphs is a very common one. I usually shop for a filter for Nissan Qashqai 2.0 gasoline -car. It fits perfectly. The oil/filter change interval for the said Nissan is 30000km for a 2.0 liter car engine, so it is more than adequate for a oil change in my America. The price is a lot lower than for a "proper" motorcycle oil-filter and I can buy one from any parts store.
Go to this page: http://m-filter.fi/tuoteluettelo.phpWhat was the part number you were using?
Obviously that's not the same, concave vs convexNapa was positive that their filter was the same as the M1-108. I compared to my stock Triumph filter,,,,, hmmmm. Not sure, but for a few bucks, supporting my local stealership and the folks that work there, I will stick with the stock filter until fall.