The invention concerns aerosol devices comprising a reservoir containing, in a cosmetically suitable medium, a multiple-block polymer (A) comprising at least a polyurethane and/or polyurea unit and a film-forming polymer (B), the polymers (A) and (B) and the device being selected so as to obtain, at the device outlet, droplets of composition with average diameter less than 80 μm. The invention also concerns a hairstyling or hair-fixing method comprising the use of said devices and their use for making a hairstyling product.