The Ghost A1 stands for "Aluminum one," which means the case is constructed by one solid piece of aluminum that wraps around the complete keyboard securing it in position.
The Ghost K1 stands for "Keyboard one"- our Ghost K1 keyboard, in contrast to our Ghost A1 keyboard, is gripped tightly by plastic and not aluminum. Ghost K1 is our entry-level keyboard to encourage anyone to pick up the keys.
The K1 PRO is our most recent iteration of the K1 keyboard. It a custom acrylic case, 5-pin Hot-swappable PCB, Double Shot PBT keycaps, and much more!