There must be a very good center tube slit punching machine salesman out there somewhere. More are going that way than not. I like the round holes better, but if the slits are open, seen by inspection, they should flow just fine. I still think it can leave more burrs. That is one more thing for the oil filter guy to remember to look at. While other customers at the store are saying what is that guy over there doing to the oil filters, or whatever those little can things are.