From Halopedia, the Halo wiki
RJM 36" 7c rims are the rims featured on the standard model of the 2553 Hog. These replace the RTPCS rims that are equipped on the factory equipped model of the 2553 Hog.
These rims have the Seventh Column on them, a symbol commonly associated with Bungie and the Bungie community. The 7c part of the name can also be seen as an abbreviation of Seventh Column.
The Standard model of the 2553 Hog with the rims on.