Measure radius of external arc, arc angle of measured surface should be larger than 90?
Resolution .0005″/0.01mm
Buttons: on/off, set, inch/mm, preset (+, -)
Automatic power off, move the digital unit to turn on power
Battery CR2032, Data outputMade of stainless steel
Supplied with pin gage for zero setting

Dynabrade 90873 2" Dia. Medium NWN DynaBrite Locking-Type Disc, 25/pack
3M 26137, PPS Series 2.0 Adapter, Type S41, Trapezoidal Thread - QCC, 7100135947
3M 35833, Hookit Dust Extraction Flexible Radius Sanding Block Kit, 7100259118
Insize 2197, LARGE RANGE DIGITAL RADIUS GAGE, R1(4-590"/100-1500mm), R2(4-590"/100-1500mm), 697409778087 