I have been through this with Baldwin customer service and tech support and have written about it several times here on Bitog. The specs of the filters they make are on their website. They get OEM oil filter specs on paper and also test several OEM filters in their engineering dept. Then they start making the filters. Baldwin openly says they are not in the micron rating-efficiency race. They do try to match the OEM efficiency and flow rates. In my case, the B33 has a nominal rating of 23 and an absolute rating of 45. It has paper media, though they do make synthetic blend and fiberglass media filters for other applications. The bypass valve is 14 psid. I have always joked about how they only catch the bird nests and small pebbles. LOL! There are a lot of Toyota owners that ran their Toyota cars over 300,000 miles using nothing but the Toyota OEM filters since the day they were new. I like the construction of the Baldwin filter better. They make heavy duty, quality, OEM specification filters of all kinds. They are owned by Parker Hanafin Corp., a USA company, and shipped all over the world. Anyhow, I like them, and I use them.