From Halopedia, the Halo wiki
The CIO helmet has a tricloptically fixed multi-spectral imaging array, also known as a transponder array. The neural interface bypasses in the CIO helmet allow the wearer to create custom synesthesis profiles to remap the suit sensors with their own senses. The suit also has a galvanized sensory suite that rivals nearly all other similar service packages.
The chest has a modular sensory suite, and a silhouette dampener for motion sensor circumvention.
After seeing the need for highly trained, heavily armored personnel to be deployed deep into enemy-controlled territory, Acheron Security developed and manufactured the CIO-class armor, with its main focus on espionage rather than lethality. The armor was tested at the Acheron Trauma Sim, and was designed to operate in the Martian territory of Acheron Fossae.
Though rarely seen, it is utilized by a handful of SPARTAN-IVs and Counter-Intelligence Operators for intel acquisition and strategic data conveyance deep within enemy territory, often those who endure tier-nine theaters.
CIO is also used during information denial missions, hunting down enemy scouts and preventing them from acquiring data of tactical or strategic importance.
Available skins: Web (WEB), Ruin (RUIN), and Rush (RUSH)
Halo 5: Guardians
Unlock: Rare REQ card
In Halo 5: Guardians due to the "Body" having a predefined customization this armor set permanently has the following parts from Halo 4:
Halo 4 skins
Halo 5: Guardians skin
Halo 5: Guardians REQ cards
List of appearances