A seatbelt retractor for a seat belt device in a vehicle. The retractor including a frame and a spool. The spool is configured to be fixed to one end of a webbing which is wound around the spool. A pretensioner device configured to rotate the spool in response to an excessive acceleration of the vehicle. The pretensioner device comprises a power transmission element carried in a pretensioner tube that is driven by a piston located in the pretensioner tube. The pretensioner device includes a gas generator for driving the piston into the power transmission element. The pretensioner device includes a seal system that includes a stopper tube located in a downstream end of the pretensioner tube to create a stop location for the piston to prevent operating gas from exiting the end of the pretensioner tube.