Below is some more information from the manufacture. 811-1CZ Dial Test Indicator with Swivel Head. The Starrett 811 Dial Test Indicator with Swivel Head is one of the most versatile and unique indicators available. The swivel head feature allows positioning to suit your line of sight from horizontal to vertical and at any angle in between 90 Deg. 060 Range, 0-30-0 White Dial.
Contact point reverses automatically, always maintaining clockwise hand rotation. Contacts are frictionally adjustable and replaceable.
Contacts also available individually in steel, carbide and different sizes. Some of the most versatile and unique indicators available.
Swivel head feature allows positioning to suit your line of sight from horizontal to vertical and at any angle in between 90 Deg. Inch reading indicators are available with white, red, or black dials - metric indicators with yellow dials. Large, 1-3/8 (35mm) dial diameter for increased readability. Attachments include dovetail body clamp, tool post holder, swivel post snug with dovetail indicator clamp, and snug and rod unit. Two positioning mounts work with dovetail test indicator accessories. Contact Point Ball Diameter (in). Contact Point Length (in):1-5/16. Contact Point Length (mm):33mm. Attachments:Dovetail body clamp (PT22429/EDP 72441), tool post holder (PT11770A/EDP 71361), swivel post snug with dovetail indicator clamp (PT22428/EDP 72440), and snug and rod unit (Inch: PT22430/EDP 72442). Contact Point Ball Diameter (mm):2mm.