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?).

3M 65489, Pro Grade Precision Ultra Durable Universal Hole Sanding Disc DUH5120TRI-10I, 5 inch UH, 120, 7100202873, 10 per pack
Insize 1120-150P, DIGITAL INSIDE GROOVE CALIPER, .87-6"/22-150mm, IP67 dust/waterproof, 6928640387401
3M 03126, General Purpose Sanding Sponge CP040-6P, Single Angle, 2-7/8 in x 4-7/8 in x 1 in, Fine, 7100101532, 6/pack 