I was looking at the cdnn investments add in shotgun news and they have some SIG SPORT MAGS for sig sauers.  The have a finger extension on the bottom of the mag.  The add says they fit all 229 pistols.

I have a 228 9mm sig and was wanting some mags like that.  Will 229 mags fit 228's?  

How do they fit?

Here's a pic.

http://store3.yimg.com/I/cdnn_1692_9797599


I think they only have .357 and .40 mags.

I know 9mm mags are interchageable between the 9mm P229 and the P228, but I don't think the .40/.357 will work in the P228.  The mag is shaped different at the top where it narrows down to the single feed from the double stack.  I believe that the magwell on the .40/.357 P229 is machined different to accept the different profile.  

I may be dead wrong, but I'd make damn sure before you sink money into any of the mags.  Know anyone with a .40 P229?  Or will your local gunshop let you just test fit a mag?  That'd be the best check.  Also, don't forget to find out if it will actually accept 9mm.  Most guns use the same mag, but Sigs use different mags for the two calibers, so they may not even accept, retain, feed, etc. 9mm.  

Ross