Machined in pairs, these blocks are precision ground to tolerances thinner than a sheet of paper to give you the flattest and squarest surface for positioning workpieces. Since they are perfectly aligned to one another, they’ll keep your workpieces level and parallel. Also known as 1-2-3 blocks, they're typically used to elevate, support, and align parts for measuring and inspecting. They're made from granite, so they won’t scratch the surface of your workpiece. They also won’t warp when temperatures fluctuate. Unlike metal blocks, these granite blocks are nonmagnetic, so they won’t interfere with sensitive electronic equipment. They come with a certificate of accuracy that's traceable to NIST.