ANy FASS users know anything about the o-ring on the water seperator filter? I was changing my filters the other day and noticed the old fleetgaurd had the standard seal around the outside of the filter but there was also a smaller seal around the inner port of the filter. It fell off and I am not sure if it was part of the Fleetgaurd or the FASS. Anyway I reinstalled it with no aparant problems. BTW, New filters are NAPA, The secondary filter seal is nicer on the NAPA than the Cim-tek. Cim-tek was a square seal and the NAPA used an o-ring. The way the FASS is groved I feel the o-ring provides a better sealing surface. I guess better is realative though I had no VISIBLE leaks before.