Subcalibre Device?

Found on GunsAmerica, are these beasties very common? This fellow is selling four.

http://www.gunsamerica.com/guns/976647868.htm
http://www.gunsamerica.com/guns/976667812.htm

Thanks
OS

No, not common. And pretty cool too! :)

Run, Run away from Surf City!

I can't comment on this piece, but they do have quite the reputation:

Someone runs a lot of "factory new" guns through there on an extremely regular basis.

Search on the jouster.com service pistol forum for more info.