Ahh, Ian, you're forgetting that we Yanks like to improve on things a tad. Our version of the Patriot is in 411mm (or 16 inch as we prefer). Oh, and we dropped the idea of having grips. ;-)
So why is it costing the Us taxpayer so much to develop this little beauty to bring down missiles,if it already exists?I do find our Us cousins quite baffling at times.