This Supply Giant no-hub coupling with a diameter of 4 inch is the extra heavy version. The main difference with a standard no-hub coupling is that it has more clamp rings for the same size fitting. Furthermore this specific part has a colored shield for signaling purposes. UPC UL and FM approved the design for meeting all applicable standards. ⚠ California Proposition 65 Warning: This product is known to the state of California to cause cancer, or other reproductive harm. For more information, go to www.p65warnings.ca.gov.