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 a UA/Type O5 enhanced armor module for the helmet and a AN/PCK-221 FARNDALE Command Network Module. 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 reminiscent of a configuration available for the ODST helmet in Halo: Reach, unlike its appearance in Fireteam Raven.
List of appearances