There is one thing that I have found though, that I don't have a good handle on yet.I've got an M11A1 that uses the 229-1 mags, which feature a follower the spring fits "into" rather than "onto".
within the SIG Sauer Pistols forums, part of the SIG Sauer Forum category; Just nabbed a P229 40/357 with the old style slide and the German zig-zag mags.
One mag base plate was the wrong style--which got me ...
My 226 9mm 15 round mags, the spring fits "onto" the follower, but my 226 .357/.40 12 round mags fit "into" the follower.
My guess is that the "newer magazines" that allow more rounds into the same size package, are using the "into" type followers.
Neither Wolffs, nor ISMI show their products on line, so you can not tell what type of springs they actually have.