From Halopedia, the Halo wiki
The helmet has a neutral face-plate contours for activity in civilian populations. It also has a XV-3 modular comm tool that prevents localized compromise. The observation and communication features of the Defender helmet are well-suited for combat actuation in urban environments.
The chest has a 12-7R feed (shield predictor system), and is a class-4 DFN chest plate.
The MJOLNIR/Defender variant was manufactured by Imbrium Machine Complex. It was tested at Anakara Resiliency Chamber. It was developed in response to the UNSC Ordnance Commission which stated the need for defense-centric armor variants, which would be used for the protection of civilian populations rather than the assault of enemy strongholds. While following the strict ruling of the commission, the armor managed to be an effective combat system.
The Defender variant is generally used on controller bases, ONI sites, and colonial populations where civil unrest is common. The placid Defender faceplate is a symbol of both UNSC oppression and protection, due to use by Spartan anti-Insurrectionist units.
Close range weapons training is common practice for users who plan to use this variant.
Available skins: Control (CTRL), and Column (CLMN)
Halo 5: Guardians
Available skins: Castle, Fortress, and Redoubt
In Halo 5: Guardians due to the "Body" having a predefined customisation this armor set permanently has the following parts from Halo 4:
Halo 4 skins
Halo 5: Guardians skins
List of appearances