Neither of the Magpul grips will fit on the C7/regular handguards without attaching a different rail.
The MOE fits the MOE handguards.
The RVG fits on a rail and has a rail that comes with it to attach to MOE and Bushmaster ACR handguards.
The ones I showed are designed to fit on the regular C7 style handguard.
I think most guys were running the C9 grip, that's what you were seeing.



























