Kinex 500 mm steel straight edge
This 500 mm long (19.69") x 40 mm wide x 8 mm deep straight edge is made from spring steel that is carefully stress relieved before grinding and lapping to ensure that it is dimensionally stable over time and with changing ambient temperature.
This straight edge is made to an accuracy level of 0 as per the DIN 874 standard, which translates to a flatness of better than 7 µm (or 0.007 mm/0.00027") along it's entire length.
These straight edges are very useful in both machine and wood shops for evaluation of flatness and machine set up. They are supplied in a plastic and foam case to protect them when not in use.