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
3M 26128, PPS Series 2.0 Adapter, Type S33, 1/8 Female, 27 Thread NPT, 7100135950
3M 66039, Push-Ins Probed Test Plugs 393-2015-50, with Grip Rings, 50 EA/Case, 7000148552
3M 37024, Extra Large Drywall Sanding Sponge 910-DDA, Dual Angle, 2-1/2 in x 8 in x 1 in, Fine, 7010375249 