Recently I restocked my filter stash:
I noticed that the new wix 51356 looked different inside.
The old ones had a spring near the adbv and a smooth bottom:
The new ones do not have a visible spring near the adbv and have a "bump" at the bottom
of the filter
is one design supior to the other or is it just cheaper to make?

I noticed that the new wix 51356 looked different inside.
The old ones had a spring near the adbv and a smooth bottom:

The new ones do not have a visible spring near the adbv and have a "bump" at the bottom
of the filter

is one design supior to the other or is it just cheaper to make?