Geometries including triangle, square, round, polygon and rhombus are standard. All of the insert geometries are symbolized using the alphabet.

However, for the metric coding, the diameter of an inscribed circle is represented by the cutting edge length using a two-digit number. Therefore, even if the inscribed circle is the same , the symbol for the cutting edge will vary.

For example, an inscribed circle of 9.525 mm (3/8 inch) is represented by the symbol 3. An inscribed circle of 12.70 mm (4/8 inch) is shown as 4.

The symbol represents the clearance angle of the insert used. An insert with a 0° clearance angle, which is shown by the symbol N, is called a negative insert. An insert with a clearance angle other than 0° is called a positive insert. Many turning inserts have clearance angles shown by symbols N, C and P.