Precise 6"-91" CAL-X-TENDER 

Converts Your 6" Caliper Into A Large Measuring Device
Cal-X-Tender readily attaches to your caliper (two set screws and 2 clamp screws) In no way detrimental to your caliper which may be quickly removed or left assembled as a permanent measuring device.
A six inch calibration rod is supplied so that exact calibration is assured.