For that point - you can have the filter tested on a bench with a controlled amount of particulate. In usual cases when a filter is made to a certain standard all parameters are "usually" followed.
e.g. if a manufactuer goes to the lengths of making a proper designed filter (money being spent) why should they cheap out on the media, for clarification you can call up or contact guard yourself and ask for its performance and specifications - you then can match it with your manufacturer.
e.g. in some engines a mircon rating of 15 is recommended - all branded filter manufacturers wanting a piece of the sales pie produce similar product but at lower price to lure the market to them - but they have to follow the exact physical attributes and media performance. If you remember I once posted a filter media of MB diesel - its literally cotton waste, bugs, twigs etc. There is another filter usually sourced from Turkey that had a sock full of cotton string - both performed the same and had the same specifications.
if a filter manufacturer supplies to an engine manufacturer according to their spec with the engine brand stamp they cannot sell the filters from their own warehouse with the same engine brand name. e.g. ball joints of mercedes are stamped with the lemforder logo and also a MB star - you can buy the same ball joint from lemforder with the star literally "ground off" - these products were made on the same line but were not sold to MB - hence they cannot use their name. If for whatever reason it fails you cannot contact MB for it, you contact lemforder (ZF) - if the original MB joint fails you contact MB. - do both have a quality difference - YES. One is "proven quality" and one is "OEM replacement part" (cheap sleazy businesses use the replacement part word to sell scrap to naive people) Its the customer's job to be smart and sift the sleazy from the good businesses.
The above is my experience with dealing with spares - hence my anti JDM bias because there is no one to contact when it fails.
Now the extreme cheap spare items are questionable - they are usually in the market to make a quick buck and exit. In this case we see the build of the leppon filter, They cheaped out on literally all aspects of it - Why would they pay monies to have better media when the rest is scrap.
