Abstract: An air-bag unit comprises a support plate (2) having an aperture (4) in it, and an air-bag (14) which also has an aperture (16) formed in it. A gas generator (7) has a radially outwardly extending flange (8) which is located so that a region (15) of the air-bag (14) surrounding the aperture (16) formed therein is trapped between the flange (8) and the support plate (2). A gas diffuser (10) is provided which, together with the flange (8) defines a diffusion chamber (18), the arrangement being such that in use of the device, gas from the gas generator (8) is injected into the diffusion chamber (18). A plurality of elongate connector elements (17) extend from a part of the gas diffuser (10) through the flange (8) and through the region (15) of the air-bag surrounding the aperture, also passing through apertures formed in the plate (2) so that the distance between the said portion of the diffuser (10) and the support plate is variable.