Airbag apparatus

An airbag assembly 4 for a vehicle 2, comprising a primary surface and an annular restraint 6 configured to control rotation of the vehicle occupants head 19, wherein the airbag assembly is configured such that the annular restraint projects relative to the primary surface when the airbag is inflated. The primary surface may be formed by a primary bag and the annular restraint may be formed by a secondary bag, both comprising internal chambers in communication with one another via one or more vents (9, fig. 2a) which may permit the flow of gas into the secondary bag and inhibit the flow of gas into the primary bag. The assembly may comprise one or more internal tethers which may extend radially. Also provided is an airbag module comprising the aforementioned airbag assembly and one or more inflators (5), and a vehicle comprising such an airbag module.