The HK45 was a candidate in the U.S. Military Joint Combat Pistol program representing Heckler & Koch, unfortunately the program was closed down and the poor gun could not manage to enter the military. H&K then turned to the police and civilian market for it. The gun is a .45 ACP pistol derived from the USP, with the most significant improvement on the grip, making it sit lower in the hand. It also features a M1911 style safety.
And now Umarex is bringing to us the exact same thing in airsoft version. It has all the same outlook features of the real one, like the "H&K" Logo and ".45 Auto" logo on the slide. The slide is in metal, the frame is ABS plastic. For those who opt for practical feature, the lower rail would be the reason you chose this gun.