M52B body armor
From Halopedia, the Halo wiki
The M52B Body Armor is the standard issue body armor that the Marines use for protection.
It was most likely developed at the end of the year 2552 due to the fact that it is not shown in Halo: CE. The new variant seen in Halo 2 features smaller armor plating and a new color scheme in addition to both minor and major aesthetic changes such as the addition of numerous pockets to the front of the chest piece, assumed to be used for carrying supplies. It is still not yet known if there are any major tactical differences, due to a lack of relevant information released concerning the specifications of the Marine body armor. In Halo 3, the original Halo: Combat Evolved design is most prevalent only with more armor plating than the Halo 2 variant. This variant still grants the humans no shielding for simple soldiers.
M52B armor crates of 12 units weigh 173 lbs. Assuming the weight does not include the crate, that would indicate that the M52B armor could weigh about 14.5 lbs.
