Starrett 55 hardened steel squares are the same as the 20 squares, except that the blades are beveled on both edges of each side, which provides an excellent visual line contact with the work. 3"¬Ã¹ (75mm) Blade, 2 3/8"¬Ã¹ (60mm) Beam. FEATURES The finest precision-checking squares - not graduated. Squareness accuracy to .0001" (0.0025mm) every 6" (150mm) The blades are beveled on both edges of each side, which provides an excellent visual line contact with the work. These hardened steel squares are used when extreme accuracy is required. The beams and blades are hardened, ground and lapped to ensure parallelism and straightness. The beam is grooved at the inner corner for clearance of burr or dirt. Made of high quality tool steel, with the finest of craftsmanship throughout. SPECIFICATIONS Made in America: Yes Blade Length (in): 3" Blade Length (mm): 75mm Beam Length (in): 2-3/8" Beam Length (mm): 60mm Material: Steel