The TGX calibration grating with an undercut edge is made by two-dimensional anisotropic etching along the (111) crystallographic planes of silicon. Typical radius of the edges is 5nm. The TGX calibration grating is intended for lateral calibration of SPM scanners, but is equally useful for detection of lateral non-linearity, hysteresis, creep, cross-coupling effects and determination of the tip aspect ratio. Calibrated pitch is 3um with a non-calibrated step height of 1um. Chip size is 5x5x0.3mm with an active area of 1x1mm. Supplied either unmounted or mounted on a 12mm AFM disc.