bbadmin, no it's a doublestack (13+1 IIRC) but they did some serious tweaking on the mags and frame to make it all the same external size (minus a few extra mm in length for the grip) as the 9mm and .40 and all the other XDs.

Cheapo, You gonna be at the next north shoot? I really like my wife's XD9 and the g21 I have is a little on the big side for me (not unmanageable, but I'm more accurate with the XD than the g21).