Reusable bag molding incorporates a rigid base A-mold and a thin, flexible membrane bag as the counter mold. The reusable bag is constructed from silicone, latex, or polyurethane and can be used to make numerous parts before needing replacement. Closed cavity bag molding (CCBM) is a variation of reusable bag molding in which a semi-rigid vacuum clamping ring is used to provide the airtight seal around the perimeter of the mold. 

Gelcoat is applied to the mold surface if required and reinforcement materials such as fiberglass, carbon fiber, or aramid are layered into the mold. Core materials such as foam or balsa may also be added to increase part stiffness. Once all materials have been layered into the base mold, the silicone bag is placed and secured, and a vacuum is drawn. Using a low-pressure resin pump, catalyzed resin is introduced through the resin ports incorporated into the bag, and the part is allowed to cure. After curing, the vacuum is released, and the silicone bag is removed. The part is then demolded and is ready for post-processing.