⟨V˞⟩ (vowel with hook diacritic) is now standard IPA for a generic rhotic vowel. ⟨Vʴ⟩ remains in use in English dialectology to indicate specific rhotic coloring in close transcription, e.g. alveolar [Vʴ] as opposed to post-alveolar [Vʵ], labiodental [Vᶹ] or uvular [Vʶ]. The obsolete IPA variant ⟨Vʳ⟩ is not used in such situations (at least for English) because it would indicate that the vowel was trilled.