RTM called resin transfer molding, it is vacuum assisted, closed molding process. Male mold plus female mold structure achieves two smooth surfaces, which is the major advantange of this process. Fiberglass reinforcement mat or woven roving is placed in the mold, then closed and clamped molds. Catalyzed, low-viscosity resin is pumped into mold cavity under pressure, until the mold is filled.