The flange end cover fixing ring is used to fix the dome cover and the flange and also used to fix the end cover and the flange. The acrylic end cover will wear out with the screws after repeated use. The fixing ring can be more reliable and durable.
Aluminum alloy processing.
The surface is black oxidized to prevent corrosion.
Four sizes of 90, 110, 130, and 160 match flanges with inner diameters of 80, 100, 120, and 150.