This standard consists of two sub-standards:
1- ISO DIN 2768-1 Standard:
This sub-standard determines the values of general tolerances of the linear and angular dimensions and radius of curvature and chamfer height according to four classes of levels: f (fine), m (medium), c (coarse), v (very coarse).
2- ISO DIN 2768-2 Standard:
This sub-standard the values of general tolerances in regard of form and posistion according to three classes or levels: H (fine), K (medium), L (coarse).
In engineering drawings, and for the untoleranced dimensions, the medium level is usually used ( "m" for the first sub-standard and "k" for the second sub-standard), and that can be expressed by writing the following in the title box: ISO DIN 2768 - mK.