Accuracy: ?2″.
To inspect protractor, taper gage, index plate, index head and goniometer, can also be used to set angle.
Made of special alloy steel, hardness HRC64, high stability, wear resistance and easy combination.
Can be combined to any angle with interval 6 seconds after combination (6″, 12″, 18″, … , 360?).

Dynabrade 78423 4-1/2" Dia. x 3/8" Very Fine DynaBrite Surface Conditioning Disc, 25/pack
3M 76625, Roloc Disc 777F, 80 YF-weight, TR, 1 in, Die R100N, 7000045621
Insize 0020-A199, VIBRATION PEN (THREE PARAMETERS), 6974029777059
3M 91004, Drywall Sanding Sponge CP-042-4PK, Single Angle, 4-7/8 in x 2-7/8 in x 1 in, Fine, 7100111452, 4/pack 