tubular inside micrometer
棒型内径千分尺，内径千分量杆

• unit time
• unit vector
• unity emissivity
• unity transmittance
• univalent
• universal angel block
• universal apparatus
• universal bevel protractor
• universal dividing head
• universal finder
• universal focus lens
• universal gear tester
• universal gravitation
• universal horizontal metroscope
• universal joint mechanism
• universal joint spider
• universal laser
• universal length measuring machine
• universal lens interferometer
• universal level
• universal machine tools
• universal measuring head
• universal measuring microscope
• universal meter
• universal microscope