Restraining device of a seat unit

A restraining device of a seat unit, said seat unit further comprising a vehicle seat which comprises a seatback defining the rear end of the vehicle seat and a seating extending from the seatback to a front end of the vehicle seat, wherein

• said restraining device comprises an airbag having a side part enclosing a side chamber and being attached to the seatback, and a front part enclosing a front chamber and being attached to the side part, wherein the front chamber is in fluid communication with the side chamber and
• wherein, in the deployed state of the airbag, the side part extends from a rear end of the side part being attached to the seatback to a front end of the side part and from a lower end of the side part to an upper end of the side part, and
• the front part extends from an outer end of the front part being connected to the side part to an inner end of the front part, and from a lower end of the front part to an upper end of the front part,
• wherein a non-inflatable retraining element extends from a first connection section being connected to the front part of the airbag to a second connection section being connected to at least one of the vehicle seat and a part of the restraining device located rear of the front part when the airbag is in its deployed state.