■ Protractor (made of cast iron), only for 817-180-02: Used to set an angle or angle measurement, measuring range: 0-180°, accuracy: ±20' ■ Square (made of cast iron): Used as 90° square or 45° square accuracy of 90° square: ±8', accuracy of 45° square: ±10' ■ Blade (made of stainless steel): Used as rule, measuring range: 300mm/12" front side graduation: 0.5mm and 1/32'' reverse side graduation: 1mm and 1/64'' ■ Center finder (made of cast iron), only for 817-090-13 and 817-180-02: To locate center of cylinders with diameter (Ød): 30-100mm, accuracy: ±0.15mm