Measure precisely and accurately on 2.2" diameter dial with 0.001" graduations and revolution counter Easy-to-read white graduations on a black dial for 1-1000 readings Supplied with NIST traceability certification, lug and flat back, and fitted case Sturdy aluminum housing stands up to workshop environments Stem diameter: 3/8 inch (8mm) with #4-48 (M2.5) thread For over 60 years, SPI has introduced innovative products to the metalworking and laboratory industries. SPI measuring instruments are durable, precise, and reliable — all backed by an Industry leading 2-Year warranty.