The Phase II+ SRG4600-505 NIST Certified  Roughness Reference Standard is a high-quality calibration standard for portable surface roughness gauges. It is serialized and offers Ra values of 119.5 and 16.1. The SRG4600-505 offers a reliable calibration tool that permits the technician to calibrate surface analyzing equipment to its peak efficiency. The SRG4600-505 shows the actual patch mean values of low and high micro-inch surfaces.

The surface of the Precision Reference Standard consists of a series of parallel, uniform, "V-shaped" grooves having an included angle of 150° between the sides. Since the surface character of the Precision Reference Standard is unlike normally machined surfaces, it is not recommended for use in visual and tactual comparison.