Abstract: A cover (1) for an inflatable bag or cushion type retaining device (6), in particular a lateral one, including at least a body (2), a mechanism for retaining the body (2) and a mechanism for fixing the body (2), directly or indirectly, to the bodywork (5) of a vehicle. The body (2) of the cover (1) is constituted by at least two layers, namely: a layer (8) permitting the shaping and the self-maintaining of the said cover (2); a layer (9) allowing the fixing mechanism to be attached to the body (2); The fixing mechanism is designed to be added on and capable of giving way under the action of the retaining device (6) when it is triggered, so as to enable the cover (1) to open without the body (2) tearing.