AIM-120B, Rb 99
The AIM-120B missile was the result of the two block AMRAAM Producibility Enhancement Program. The B-model incorporates a new digital processor, erasable programmable read only memory, and five major electronic unit hardware chassis upgrades. The Swedish AIM-120B's, carried by the 'Gripen', are designated as Rb 99.
AIM-120C
The AIM-120C will include a redesigned warhead and improvements to the rocket motor, fuzing logic, guidance algorithms, and ECCM logic. Modified for internal carriage on the F-22, the AIM-120C will have "clipped wings" to reduce its box size from 17.4 to 12.5 inches.
From http://www.f-16.net