Safety belt pretensioner

The device has a housing part (12) with an elongated cylindrical tube (18) in which a piston (14) is arranged to be movable and a drive (16) that can exert a drive force on the piston. The housing part is T-shaped with a foot section (20) extending transversely from the cylindrical tube, formed in one piece with the tube and forming an accommodation chamber (30) for the drive. An independent claim is also included for the following: (a) a method of manufacturing an inventive device.