The heavy square base ensures stability and precision,you will love the weight, balance and design of this engineer square. The blade is permanently fixed to the beam by means of tapered self locking rivets which ensure complete rigidity.Blade edges and beam faces are precisely ground and polished for straight and smooth,have an inside notch for accuracy. This machinist square accuracy reaches DIN 875 Grade 1, it is THE square that you proof everything else to. Specification: Material: Hardened Steel(45 Steel) Precision: DIN 875 Grade 1 Size: 63x40mm(2.5x1.6 inch) 80x50mm(3.2x2 inch) 100x63mm(4x2.5 inch) 160*100mm(6.3x4 inch) Use For: Suitable for use in laboratory;woodworking, precision layout work and machine set-up Package Included: 1 x Machinist Square Set NOTE: 1. The square comes in a plastic case and wrapped in clear plastic with oil on it for protection, it's very easy to wipe off with a towel before use. 2. We recommend to store it back in it's case after use it,so that makes sure it will always remain THE standard of square for you. Manufactured to German DIN 875/1 standards, designed for precision layout, machine set-up and laboratory use This square set is made of 45# steel, hardened, tempered, beams and blades are lapped and polished for straightness and parallelism; The blade is permanently fixed to the beam by means of tapered self locking rivets which ensure complete rigidity Squares are true right angles both inside and outside Set includes 2 inch, 3 inch, 4 inch and 6 inch square The included plastic case protects your square's precision during transport and storage