60 Day 100% money back guarantee. Custom-built step height reference featuring three Mitutoyo steel gage blocks (1.10 mm, 1.50 mm, 1.80 mm) permanently wrung and bonded to a Van Keuren 3C optical flat inside a compact wood case. Provides a nominal 4.40 mm precision step for calibrating contact or non-contact measurement systems, optical profilometers, interferometers, microscope Z-axes, or CMM masters. Optical flat offers high parallelism for repeatable referencing; steel blocks are Grade AS-1 equivalents. Perfect for quick shop-floor checks, lab validation, or fixture setting where space and repeatability matter. Sold as shown, no accessories or certification included. Keyword Block: height standard, gauge blocks, optical flat, metrology reference, step height, interferometer calibration, profilometer master, van keuren, mitutoyo