In most languages, this rounded vowel is pronounced with protruded lips ('endolabial').

It is typically transcribed in IPA simply as ⟨u⟩ (the convention used in this article).

Another possible transcription is ⟨uʷ⟩ or ⟨ɯʷ⟩ (a close back vowel modified by endolabialization), but that could be misread as a diphthong.

Some languages, such as Japanese and Swedish, have a close back vowel that has a distinct type of rounding, called compressed or exolabial.

The spread-lip diacritic ⟨  ͍⟩ may also be used with a rounded vowel letter ⟨u͍⟩ as an ad hoc symbol, but 'spread' technically means unrounded.