K&N Filter
I used the HP1002 as recommended by Casper Labs (they mfg Lycoming 90 degree adaptors). I was told this filter used to be a certified filter when owned by the previous company (don't remember the name). K&N continues to build it to the same spec...thicker metal can for higher pressure, lock wire tab, better check valve location than the Champion to prevent returning trapped stuff back to the oil system. The smaller size of the filter allowed me to use it on my O320 powered 4 with the 90 degree adaptor and clear the motor mount.