UNC & UNF Thread Measurement:
Designed to accurately measure both UNC (Unified Coarse) and UNF (Unified Fine) thread sizes.
Length and Diameter Measurement:
It’s suitable for measuring the length and diameter of UNC, UNF, Metric, and SAE.
Quick Size Identification:
Enables fast and easy determination of the exact length, width, and diameter of nuts and bolts.
Precision Measuring Tool:
Constructed from ABS plastic for accurate measuring. It also includes SAE to ISO hardness conversion.

Read more here