sGroup:

sGroup is a group of surfs/sSurfs to make a larger surface. When unassigned, these sGroups will only be visible 3D meshes attached to the main vehicle body and not have any mass, collision physics or aerodynamics. When assigned to a body panel, these will become a body panel having mass, collision physics and aerodynamics. If you assign a sGroup to a body panel with an underscore '_', like '_Bumper F', the sGroup will become a visible 3D mesh attached to that body panel and not add to mass, collision physics or aerodynamics.