·Achieve narrow and small inside groove
·The optional presetting electronic comoponets make the measurement convenient and not affect the reading result after weariness.

·Available with digital, vernier and dial types.
·Special-made required following data:
1.The diameter of the hole
2.The distace from the groove to the orifice
3.The width of the groove
4.The depth of one-sided groove
5.The shape of the slot base