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 78293 3" Dia. x 2S Fine, Type R Unitized Locking-Type Disc, 25/pack
Dynabrade 92210 1/8" W x 12" L 320 Grit A/O DynaCut Belt, 50/pack
3M 27704, Cubitron II Roloc Durable Edge Disc 984F, 36+, YF-weight, TSM, Maroon, 1-1/2 in, Die RS150SM, 7000045168, 200 per case
3M 37024, Extra Large Drywall Sanding Sponge 910-DDA, Dual Angle, 2-1/2 in x 8 in x 1 in, Fine, 7010375249 
