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 the UA and CNM helmet attachments. The armour's component pieces are capable of being employed on the Mark VI MJOLNIR platform. The ODST/HVY armor is rated for vacuum, allowing operators to perform short spacewalks on the exterior of spacecraft when needed.
Halo: Fireteam Raven
The ODST/HVY armor is worn by players playing as Victor Ramos. It confers no in-game effects.
As of Season 6: Raven, the ODST/HVY is available for use as an armor permutation in the Halo 3 component of Halo: The Master Chief Collection. The helmet of the HVY variant comes equipped with the UA/CNM attachments, unlike its appearance in Fireteam Raven.
List of appearances