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 26006, PPS Series 2.0 Adapter, Type S5, 12 mm Male, 1.5 mm Thread, 7100135831
3M 26120, PPS Series 2.0 Adapter, Type S28, 17.5 mm Female, 19 TPI
Thread, 7100135956
3M 26018, PPS Series 2.0 Adapter, Type S11, 3/8 Male, 18 Thread NPS, 7100135942
3M 26141, PPS Series 2.0 Adapter, Type S44, 3/8 Female, 19 Thread BSP, 7100158892
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 
