This is a new design for the GLOCK 21 .45 ACP pistol. GLOCK redesigned it with a smaller grip (Oirgnal large even for folks with big hands. Now it's about the same as a GLOCK 17), new redesigned ambi-magazine release, and lastly a M1913 Pictinny Rail instead of the GLOCK Universal Light Rail.
In the end, selling my old GLOCK 21 and getting that.