O/I optics device
From Halopedia, the Halo wiki
The O/I (Ocular/Integration) optics device is a helmet attachment worn by snipers in the UNSC Armed Forces. They are employed by ODST donning the sharpshooter variant of the ODST armor and UNSC Army personnel.
During the Fall of Reach, O/I devices were worn as attachments UNSC Army soldiers' CH252 helmets and the ODST helmets worn by the ODSTs. During the Battle of Mombasa, ODST sniper Kojo Agu employed an O/I module on his helmet.
Installation 07 conflict
List of appearances