This page contains information regarding new Star Trek material, and thus may contain spoilers.
The D4 class was armed with two directed energy cannons on top of the wings near the fuselage. The homing green energy blasts from the cannons could arc through the air before impacting a target. The engine had a single aft exhaust. The wings could be angled in various ways, giving the ship high-speed atmospheric maneuvering capabilities and allowing it to maneuver through tight spaces. The ship had landing capabilities. Troops from the ship could also be deployed on cables mid-flight from four hatches in the underside of the craft. (Star Trek Into Darkness)
In 2259, three of these vessels intercepted the K'normian trading ship that was confiscated by the crew of the USS Enterprise during the Mudd Incident. The trade ship was carrying James T. Kirk, Spock, Nyota Uhura, Hendorff and another security officer over the Ketha Province on Qo'noS. The D4 class ships forced the trade ship to land. The ships were later destroyed by Khan Noonien Singh. (Star Trek Into Darkness)
Concept artist James Clyne designed the original sketch for the D4 class Klingon fighter. Pixomondo heavily detailed the industrial-type fighter ship design and gave it a "Bird-of-Prey" feel. Visual effects supervisor Ben Grossmann has stated that the ship was designed “..not in the traditional namesake of the Klingon Empire, but more of like, you can imagine this chase scene as an unarmed trade ship and a bad-ass predator. You had this larger more predatory hawk chasing a little sparrow trying to take advantage of its size and move through little cracks and nooks and crannies and be a little more nimble.” 
In "Unexpected", Vorok's battle cruiser was originally designed by John Eaves to be a prime universe counterpart D4 class starship. However, the K't'inga-class CGI model was reused to represent the ship when it appeared in the episode.