See the Nord-Lock Promotional Video
W4ABC's M2 OR2800 on the bench.
M2's Caution Notes on the subject...
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Dimensions...
Dimensions and Relationships...
We're going to use two SKU #0162563 1/4" Nord-Lock Locking Washers...
You are NOT looking at four Nord-Lock Washers.  Each one is constructed of two identical halves.
The 1/4" Nord-Lock Washer with an outside diameter of .450 is a perfect fit.  The combination drops easily into the cup of the Mast Centering Device.