3M 82975, Roloc D/F Cool Running Disc Pad TR, 3 in 1/4-20 Internal, 7010309116 
Insize 2187-108, ADJUSTABLE SNAP GAGE, 3.98-4.25″, 6928640314520
$263.41
Used as Go/No-Go gage by setting upper and lower limits.
Flatness of anvil: 59_in.
Parallelism between tips and anvil: range 0-1.26″: 118_in,
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