USSF-8 debuted a new variant of the Atlas 5, the 511. This version has a five-meter fairing, only one solid rocket booster, and one engine on the Centaur upper stage. The single solid rocket booster is possible because the nozzle is angled through the average center of mass of the rocket, and the RD-180 main engine has a large gimbal range to compensate for the offset thrust. The 511 variant has always been available, but until now, no payload has needed it.
USSF-8 included two GSSAP or Geosynchronous Space Situational Awareness Program satellites. Not much is known about the two satellites except that they will monitor objects, including active satellites and space debris, in geostationary orbit. USSF-8 included the fifth and sixth GSSAP satellites. The first four were launched on now-retired Delta IV Medium rockets.
ULA press release