Dynabrade 51756 .1 hp Straight-Line Extension Pencil Grinder, Rear Exhaust, 35,000 RPM, 1/8" Collet 
Insize 1129-300, DIGITAL DEEP HOLE INSIDE GROOVE CALIPER, 0-12″/0-300mm, 6928640392528
$580.54
Resolution .0005″/0.01mm
Measure diameter of grooves inside deep holes
Buttons: on/off, set, inch/mm, preset(+,-)
Automatic power off, move the digital unit to turn on power.
Battery CR2032. Data output.
Made of stainless steel.
Optional accessory: data output cable