with reference to the shoulder 55 of the vehicle occupant 30 with a differentiation having been made between large and small vehicle occupants with reference to their shoulder height h u2032 and h u2033 respectively of course other body parts or body proportions or body dimensions can also be used in order to differentiate between large and small vehicle occupants for example the body width or torso width can be used as a measure with u201c broad u201d vehicle occupants being regarded and treated as u201c large u201d while u201c slender u201d vehicle occupants are regarded and treated as u201c small u201d fig8 to 11 show a third embodiment of the present invention in fig8 a side airbag 10 with two chambers 100 and 110 can be seen the upper chamber 100 is a head chamber which protects the vehicle occupant 39 s head in the event of an accident the lower chamber 110 is a thorax chamber which protects the upper and lower body of the occupant in addition an overflow opening 130 which permits a gas flow between the two chambers 100 and 110 can be seen the cross section or diameter of the overflow opening is determined by the size and positioning of a tuck which is indicated by the reference number 140 in the event of an accident the side airbag 10 is inflated by means of a gas generator 150 during inflation the gas generator 150 fills both the head chamber 100 and the thorax chamber 110 as indicated by the arrows 160 in fig8 fig9 to 11 show the functioning of the side airbag 10 of fig8 over the course of an accident in fig9 a side wall 40 is pressed.