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. Stainless steel construction: all measuring surfaces are surface-hardened. Preloaded dual pinions eliminate backlash and provide better repeatability. 4-way measurements: inside, outside, depth, and step. Easy zero adjustment per revolution. Adjustable bezel with locking device. Covered rack keeps gear teeth clean. Includes thumb roller, short form calibration certificate, and fitted case.