the invention relates to a blowing or stretch - blowing device for making vessels from thermoplastic blanks with a collar , that comprises a blowing nozzle mobile between an upper position and a lower position for blowing a pressurised fluid into a blank having a body provided in the moulding cavity of a mould and having a collar protruding outside the mould , the device includes a clamping means provided above the mould and capable of holding a blank by the collar thereof , a holding means for the clamping means for moving the same between two raised or lowered positions , wherein at least one branch of the clamping means being transversally mobile ; mechanical coupling means provided between the clamping means and the blowing nozzle and capable of synchronising the movements of the clamping means with the movement of the blowing nozzle .