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?).

Insize 4120-12, METRIC THREAD RING GAGE, GO, M12x1.75, 6928640341472
3M 65491, Pro Grade Precision Ultra Durable Universal Hole Sanding Disc DUH5220TRI-10I, 5 inch UH, 220, 7100202878, 10 per pack
Dynabrade 95842 Dynabrade Air Lube 10W/NR, 1 Pint 