Pre-drilling on glass/acrylic not required Left: For left-lower/right-upper Right: For right-lower/left-upper GPH-40R-G and GPH-40L-G should be used with the socket PHB4WARNING: This product can expose you to chromium, nickel, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65WARNINGs.ca.gov.