Die-cast. A section for 4L or 1/2" x 11/32" belts. All pulleys are furnished with hollow head set screws. The 146 3-step pulley measures 2-1/4", 3" and 3-3/4" outside diameter. The 141 4-step pulley measures 2", 2-1/2", 3-1/2", and 4" outside diameter.