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AA-Ring Opening BB-Seat Dimension F-Ring Height Rise Shape
23 1/2 1 1/2 3 1/2 2 Round
All dimensions are listed in inches unless otherwise noted.

Heavy Duty

Adjusting Rings or extension rings, as they are sometimes called, eliminate the necessity of raising or replacing existing manhole frames on resurfacing projects.   The cover recess is

the same depth and diameter as the existing manhole frame.  Amount of raise coincides with thickness of resurfacing material, thereby bringing the manhole lid to new position flush with

refinished roadway surfaces.


Be sure the existing lid diameters are smaller than “AA” dimension in table.  The “AA” dimension opening size in extension ring.  Lid should measure 1/4″ to 3/8″ less in diameter than this dimension.

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