From Halopedia, the Halo wiki
The MJOLNIR Powered Assault Armor/C variant, colloquially known as the Close Quarters Battle (CQB) armor, is a variant of the MJOLNIR Powered Assault Armor manufactured by Beweglichkeitsrüstungsysteme.
The CQB variant specializes in the improvement of survivability in close quarters engagements, this was done in the dispersal of kinetic energy, by looking at alternate methods to disperse the kinetic energy versus momentum transferred by a Spartan during combat. In addition the CQB's armor components are designed to optimize joint mobility in close quarters, and have an improved field of view.
As early as 2525 developmental Mjolnir permutations utilized physical architecture that would eventually be used for CQB. Samuel-034 used such a variant during the Battle of Chi Ceti and Daisy-023 used a similar variant.
When evaluating different opportunities to improve MJOLNIR across an assortment of engagement types, German-based Beweglichkeitsrüstungsysteme proposed two distinctive variants CQC and CQB with one focus. Using data gathered from the UNSC's campaign on Jericho VII, that focus was to further improve the survivability in close quarter engagements.
Field-tested at the Special Warfare Center Essen, in Deutschland, and integrating feedback gathered from the Special Warfare Center Seongnam, in Korea, CQB was ultimately launched as a successor to CQC on the Mark V platform. Its advances were eventually incorporated into the Mark VI series.
The CQB armor was used successfully throughout 2552.
Halo 3 - Mark VI GEN1
The CQB armor permutation is one of the default unlocked armor sets available in Halo 3.
Halo: Reach - Mark V GEN1
The CQB helmet is available as an unlockable helmet armor permutation in Halo: Reach. Alongside the Military Police helmet and UA/Base Security [W] chest, it cannot be unlocked in Halo: Reach through regular in-game means. Instead, it is unlocked by completing achievements for Halo 3 and Halo 3: ODST and career milestones on Halo Waypoint. Following the shutdown of Xbox 360 Halo online services in December 2021, this achievement will no longer be attainable.
Halo 5: Guardians - GEN2
List of appearances