When I started having problems with the hydraulic pump on my dozer, I put in a new Case hydraulic filter. It was $80. Not too long after that they pump got worse and I pulled it out for a rebuild. When I replaced it, I also replaced all three hydraulic filters. I thought Case was a little on the high side for filters, so I bought Napa filters for half the price.
I cut open the Case filter looking for metal particles or other clues as to what might be the problem with my hydraulic pump. Then for some reason, I saved the filter. I don't remember why, but it turned out to be an interesting desicion. A year or so later, I had another problem with all three hydralic pumps slowing down at the same time, right after the engine warmed up. I pulled one filter off and cut it in half. That wasn't the problem, but I did compare the Napa Filter to the Case OEM filter.
The Napa Filter had an extra metal screen and a much finer mesh like material. There was also more of a paper like material betweent the mesh stuff. Too me, it appeared to be a much better filter.
Eddie