A two component primer surfacer that has exceptional filling capabilities and patented 4:1 mix ratio technology. it is ideal for holding down troublesome repairs on fiberglass and SMC. super build 4:1 passes 500 hr in salt spray tests (ASTM b117) and can be applied over properly sanded and cleaned bare metal. it is compatible with waterborne paint systems and VOC compliant. must be catalyzed with 733 4:1 polyester primer catalyst or 734 fast polyester primer catalyst only.