The AR12 is a 12 inch Beautydish reflector that has a center deflector that blocks the light coming directly from the flashtube. That creates a softer looking image without the normal specularity of a small flash.
In addition to being 12 inches across the front and thus more than four times bigger than the normal reflector, it also includes a cloth diffuser for an even softer look.
Lastly, a grid is included that snaps into the front of the reflector and limits the light output to less than 50 degrees.