A guide that can be included as part of a pretensioner for a motor vehicle belt restraint system. The pretensioner includes a frame having walls that define an interior compartment. Located within the interior compartment is a piston assembly having a gas generator in communication with a piston. The gas generator creates an expanding gas that causes movement of the piston and applies tension to a seatbelt of the belt restraint system. The guide includes an opening through which the seatbelt passes and that causes the seatbelt to form a reduced width configuration upon exiting the guide.