Depending on the emissions or gas residue given off during molding, the molder may have to evaluate whether to use a 7 or 20 micron pore size. Resins such as ABS, polypropylene, soft PVC, polyethylene, acrylic, polyurethane, and polystyrene work very well with a 7 micron (.0003") pore size. For low viscosity or talc filled resins, it may be necessary to have an automated system reverse the airflow after each shot to purge the impurities from the pores. NOTE: Rigid PVC resins will work with limited success until the corrosive gases close the pores. This can still be a feasible method if disposable Porcerax II® inserts are used. Please note the 20 micron pore size (.0008") will vent about 25% more gas than the 7 micron pore size.