Rounded Font

Filter → Rounded Font rounds the stem endings with appropriate overshoots. For this, it uses the vertical stem metrics as defined in File → Font Info… → Masters → Stems. The custom parameter rule is as follows:

RoundedFont; Vertical Stem Width

If a Vertical Stem Width argument is set, its value is used instead of the vertical stem width from the master metrics. Such an override can be helpful when combined with the include and exclude arguments to define a different stem width for a subset of glyphs. For example, consider three Filter custom parameters for an instance:

RoundedFont; exclude: f, k, t, dollar, percent
RoundedFont; 74; include: f, k, t
RoundedFont; 86; include: dollar, percent

Here, the glyphs f, k, t, dollar ($), and percent (%) would be processed with special Vertical Stem Width values. See Filters as Custom Parameters for details on include and exclude.