Iso 2768 -2 |top| «99% Reliable»

In Class H, a 100mm surface has a flatness tolerance of 0.1mm. In Class L, that same surface allows for 0.6mm. 2. Perpendicularity

ISO 2768-2 is titled “General tolerances — Part 2: Geometrical tolerances for features without individual tolerance indications.” Its primary function is to establish a standardized set of default tolerances for features that are not individually annotated. Without this standard, a drawing might need a tolerance callout for every single edge, surface, and profile, leading to "drawing pollution." By applying ISO 2768-2, the designer implicitly communicates that any feature lacking a specific geometric tolerance (such as flatness, straightness, or symmetry) need only meet the "general" standards of the specified tolerance class. iso 2768 -2

Here's an essay on the topic: