CH252 helmet
From Halopedia, the Halo wiki
The CH252 Helmet is the standard issue UNSC Marine helmet. What appears to be an earlier version of the helmet is used by the Marines stationed at the Pillar of Autumn, and an even earlier is seen used by the Marines stationed at the Spirit of Fire.
There are several versions of the helmet seen worn by different different field specialists. The standard helmet weighs about 3.3 pounds according to crates found in the game, and is painted olive to match the standard issue UNSCMC body armor. This version can be fitted with ballistic goggles, in either orange or black, although the latter appears to be most most commonly found on sergeants or squad leaders. The ballistic goggles are more common if the Halo 3 thunderstorm skull is turned on. In Halo 2 and Halo 3, you can shoot off their helmets. They will not pick them back up.
The standard issue helmet fitted for the ODST body suit sports a slightly shorter brim, with a full covering reflective faceplate with HUD supporting abilities. The ODST version is made out of titanium armor, and features a matte black trim to match the body suit and is sealable to be used in hard vacum. It is unknown if the standard UNSCMC helmet and pilot helmet are made out of titanium as well, or polymer, although considering the weight the former is more likelly.
The Marine pilot helmet is another version of this type of helmet. This was most likely manufactured around the end of 2552. It is not seen until Halo 3. This helmet is almost a replica of the ODST helmet. It features HUD support and weighs about 4 pounds. It features a olive trim like it's standard marine counterpart, and has a black or clear visor. Each also bears a wing symbol, likely denoting their particular speciality.
According to the description for the ODST helmet permutation, UNSC combat armor, including that used by the UNSC Marine Corps, utilizes CTC's for protection enhancement.Template:Fact By 2553, This helmet became common.