ex
The height of the lowercase x — typography's middle line, turned into a unit.
One ex is the x-height of the font in use: the height of the lowercase letters without stems or descenders, the core the eye runs along. It is one of the oldest units in CSS, and the standard keeps the usual emergency exit: with no reliable metric, it is worth 0.5em.
It is the right choice for ornaments that must match the lowercase: a marker embedded in text, a hand-drawn highlight, a superscript offset in ex rises in proportion to the font — swap the family and the alignment rebuilds itself.
xx
.grifo {
display: inline-block;
height: 1ex;
}