In at least one embodiment of the present invention, a seatbelt pretensioner is provided. The pretensioner comprises a cylinder having a proximal section which defines a gas chamber that forms at least a portion of an interior space defined by the cylinder. Extending distally from the proximal section is a guide section. Disposed within the interior space is a piston that is moveable toward a distal end of the guide section. The piston has a proximal portion and a distal portion that extends from the proximal portion. The proximal and distal portions are disposed respectively adjacent to the proximal and guide sections. The distal portion is configured for attaching to an anchor that is coupled to webbing of the seatbelt. In fluid communication with the gas chamber is a gas generator. The gas generator is configured for generating gas to move the piston, tensioning the seatbelt.