The Napa and Wix filter went through a cost cutting measure a couple of years ago
and Manf. was sent overseas to a "one size fits all" type of thing.
That's why they no longer fit well.
Sock filters are supposed to fit tight but not that tight.
The Baldwin JC 405 made in USA fit tight but much better due to it being
closer to original specs.
More reading if interested from
http://www.t137.com/swish-e/swish.cgi?query=sock+filter&submit=Search%21&metaname=swishdefault&sort=swishrank&dr_o=12&dr_s_mon=1&dr_s_day=12&dr_s_year=2015&dr_e_mon=1&dr_e_day=12&dr_e_year=2015