From Halopedia, the Halo wiki
The HVY variant of ODST armor bears resemblance to the late war design of the armor, with a notably boxier design. The front is equipped with multiple ammunition pouches, and additionally comes equipped with an ammunition backpack and a combat knife. The helmet is capable of equipping an External Hardened Uplink module. The armour's component pieces are capable of being employed on the Mark VI MJOLNIR platform. The ODST/TAC armor is rated for vaccuum, allowing operators to perform short spacewalks on the exterior of spacecraft when needed.
Halo: Fireteam Raven
The ODST/TAC armor is worn by players playing as Ethan Graves. It confers no in-game effects.
As of Season 6: Raven, the ODST/TAC will be available for use as an armor permutation in the Halo 3 component of Halo: The Master Chief Collection. In Halo 3 the helmet has a HUL module attached, unlike the version seen in Fireteam Raven.
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