Two inside micrometers (internal micrometers), also called bore micrometers. The brand is Mitutoyo, which is a Japanese company known for high-quality measuring tools.
Function:
They are used to measure internal diameters with very high precision, for example in:
• Drilled holes
• Bearing fits
• Pipes and cylinders
Details:
• The scale shows measurements with 0.005 mm resolution, making the tool extremely accurate.
• The small window shows full millimeters digitally (mechanically), while the rotating drum shows the fine reading.
• They have three expanding measuring arms that press evenly against the inside of the hole.
• The measurement range is visible on the body, for example 45–50 mm.
Summary:
These tools are often used in manufacturing, workshop and quality control where very precise internal measurements are required.