See this thread.....
www.sigtalk.com
Look what I got- 10 round magazine! (Prototype)
The shorter one is obviously just a standard P210 magazine that came with my Standard. The longer one is an extended magazine for a P225 which holds ten made by ProMag (yes, yes, I know). I was able to file the notch some and it now locks into the pistol, and during initial hand-cycling appears...