VEHICLE AIRBAG

An assembly includes a seat back having a top end. The assembly includes an airbag supported by the seat back and inflatable to an inflated position including an inner panel and an outer panel defining an inflation chamber therebetween. The assembly includes a plurality of support tubes inflatable to inflated positions extending from the seat back along the outer panel, at least one of the support tubes in the inflated position extending from the top end of the seat back.