Extra smooth movement: dual pinion mechanism provides smooth operation Sturdy aluminum ergonomic die cast housing can be used in the harshest of manufacturing environments including situations with hot steel chips Accurate to 0.0010"; 4-way measurements: inside, outside, depth, and step Shockproof design Short form calibration certificate and fitted case are included 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.