I was wondering the same thing myself just recently. I got a bunch of info back from Baldwin, but no reply from Wix.
I got the Beta ratings back on the Wix filters for my application. I am sure other automotive applications would be similar. They are as follows:
22 micron (BX=2), 45 micron (BX=75) and (I am not sure what this one means) 1.1 (B10 = X).
It also stated that it had an average efficiency of 72.20%, and an established micron rating of 22 microns. The burst rating is 200 psi, and the collapse rating is 100 psid.