Extensions can be added to both the 780XT and 78XT Series, enabling internal measurements in deep hole bores. (Multiple extensions can also be used.). 6" Length.
Internal Micrometer Extension, 3/4-2" (20-50mm), 6". The Starrett Internal Extensions for 78 Series Internal Micrometers includes 3/4-2" (20-50mm) sizes, 6" extension size, and fits models 78XT/780XT/781XT-1 thru 2. Extension 6"/150mm Long for use with 78/780/782 -1 thru 2.