Two co-reactive resin streams are mixed immediately adjacent the entrance (54) of an impregnation die (52) used to make products by the pultrusion process. The mixing occurs immediately adjacent the fibers as they are pulled into the central duct opening (58) of the die. The resin streams are delivered to the entrance of the impregnation die by use of a resin feed head (72) positioned at the inlet of the impregnation die. An ultrasonic driver (116) coupled to the resin feed head vibrates and agitates the resin streams impinging the fibers so as to thoroughly wet the fiber bundle prior to its passage through the die.