Support and align workpieces for precise measuring and inspecting. Made of black granite, these inspection parallels won’t rust or warp from temperature changes, and they won’t scratch surfaces. Unlike metal inspection parallels, they’re also nonmagnetic, so they won’t interfere with sensitive electronic equipment. Made in pairs, these inspection parallels are precision ground to tight tolerances for matching flat surfaces on two or four sides. They come with a certificate traceable to NIST confirming their accuracy.