Fowler Hardened Steel Square Set 52-432-012-0 Made of the finest carbon tool steel, these economy squares have true right angles both inside and outside Beams and blades ground and lapped for straightness and parallelism Hardened blade Beam grooved at inner corner for clearance of burrs and dirt Squareness of blade edge to the working face: 2" & 3" = ± 0.0006" ,4" & 6" = ± 0.0008" , 9" & 12" = ± 0.0012 Description : 6" Square only