Also known as test indicators, these have a lever-style contact point that pivots as it comes into contact with a surface and a balanced dial with positive values on one side and negative values on the other side. They have highly sensitive, wear-resistant jeweled bearings for a long service life. Rotate the dial face for viewing at multiple angles. Use the included dovetail-to-stem and height gauge/tool post attachments with the swivel clamp to mount the indicator.