Double action, self centering, for measuring inside diameters, widths of slots, etc. Contact points are hardened and precision-ground to a radius.

Set of 6, in a plastic wallet with the following range: 5/16 - 6”

5/16         to ½”

½         to ¾”

¾         to 1¼”

1¼         to 2-1/8”

2-1/8 to 3½”

3½         to 6”