I know I've said this before, but here it is again- the 51515R is a race filter using a less restrictive filter media, rated at 28 gallons per minute through larger bearing clearances for engines that live their lives above 5,000 rpm. A 60 micron particle is large enough to damage a bearing at the clearances our street engines are built.
The Wix 51515 is rated at 290lbs burst strength, has an anti-drainback valve, is rated at 7-9gpm (more than enough for even a 30mm oil pump in an aircooled VW street engine) and will trap particles almost 1/3 the size of the race filter. The equivelant Napa, being made by Wix, is the same. I see no reason for there to be particles that large floating around our engines when there are filters so much more suited for our use.
And David, I can relate!