Abstract: A low cost pretensioner is provided by using an ignitable charge and initiator integrated with a piston which is disposed in a cylindrical metal tube that has a common straight gas generation and piston travel bore so that a inexpensive metal tube rather than a complex casting can be used. A cable is connected at one end to the piston and passes through a cable deflection device having a locking device for locking the cable against travel in a reverse direction after tightening the seat belt system. The locking device may be an inexpensive, one-piece wedge-shaped clamping or gripping device which transfers the high tensile forces from the passenger's body pulling on the cable through the deflection device to a vehicle anchorage rather than through a locking device which is disposed within the cylinder tube which must have tube walls sufficiently strong to withstand such high tensile forces.