For this new generation of VP9A1 handguns, HK kept the great ergonomics but removed the finger grooves seen on previous models, extended the ambidextrous slide lock/release levers, and cleaned up the trigger.
The 4-inch barreled VP9A1 K has a compact slide and frame... (All photos: Seth Rodgers/Guns.com)
The VP9A1 K, or simply the VP9K, is a compact version with a shortened frame similar in size to a Glock 19. The VP9A1 X, or VP9X, is comparable to a Glock 19X, with a compact slide but extended grip frame. Both models are optics ready.
...while the VP9A1 X keeps the compact slide but has an longer grip frame, seen here with an extended mag.