4-Inch Plastic Quick Coupling / Disconnect Blast Gate for Vacuum/Dust Collector, Big Horn, Mfr#: 11441$6.55+
4 Inch Vacuum Metal Dust Shroud Cover with 1.75 Inch ID & 1.25 Inch Vacuum Connector, Hardin, Mfr#: DC4$24.99+
4-Inch ABS Plastic Wall Mounted Blast Gate with One Threaded End & One Quick Disconnect End, Big Horn, Mfr#: 11457$9.59+