The D7-class was a class of Klingon Warship notable for being in service from the 22nd through 24th century. They have two disruptor cannons and two torpedo tubes (One forward, one aft). It is about 228 meters long. They were the backbone of the Klingon Imperial Navy during the 23rd century before being superceeded by more advanced spacecraft such as the K'tinga and Vor'cha-class cruisers.
The D-7 class Cruiser is a versatile combat warship that appears to be easily upgradeable, as indicated by the longevity of the class in operation. It is seen to be a robust design and very capable of holding it's own against the Federation's Constitution-class ships. The vessels may have had massive upgrades in response to the Federation's deployment of the Miranda-class and the Constitution Refit program in an attempt to keep the pace with those vessels. The ship was phased out of service with the deployment of the B'Rel-class Bird of Prey
The D-7 class cruiser is armed with heavy disruptor cannons in the foreward ends of their warp nacelles, a forward torpedo tube mounted below the command deck in the boom of the ship, and an aft torpedo tube mounted in the raised structure at the centerline of the ship. Three D-7 class ships can easily overwhelm an unprepared Constitution-class ship.
The vessel has been observed in the service of the Romulan Empire as part of the Klingon-Romulan Alliance during the TOS era. The Romulan versions of the ship are confirmed to be capable of mounting and operating a cloaking device. There is no indication that any Klingon-operated vessels used cloaking devices until the 24th century. A Romulan D-7 cruiser was part of a Federation covert operation to steal an operational cloaking device.