A Cannon specifically developed kit to be added to the dosing unit, enables surface post injection on HP-RTM parts in order to reach higher surface quality. The device allows to store mixed resin during the injection phase and to release it at the desired rate during the curing phase after the principal injection is ended. This procedure allows to compensate the chemical shrinkage affecting the resin, avoiding therefore unaesthetic defects on the demoulded part surfaces. Cannon modular design permits the shrinkage recovery of parts containing the widest range of resin volume and shape complexity.