Profile: Diamond Plastics, Inc. specializes in manufacturing rotomolded components for original equipment manufacturers. We provide assistance with mold design, insert molding, assembly and mold-in graphics services. We can rotomold all parts from the smallest to the largest, and fit them to the proper size rotational molding machine. Molded-in inserts such as castings and stampings are available for rotomolding components. Spinwelding is a method of attaching fittings to rotationally molded plastics by friction welding, that eliminates the need for trying to tap a pipe thread into the wall of a plastic part. This can replace costly bulkhead fittings.