This is a sample from a outdoor power equipment filter I commonly use. The John Deere as resent as last year was an e-core design and about $7. The Napa/Wix was a steel tube with holes in it last time I bought one (also about a year ago). The Kawasaki filter is a direct copy of the Deere filter but with an orange ADBV. Both are made by Champion and the OEM filter pulled off had an e-core center tube as well. This batch all have louvers and all look horrible. The wix made filter has visibly closed ones. I’m probably going to go with a Champ full sized version of the ph3614 style filter that still has the nylon cage. Having oil present is more important than efficiency in my opinion.