All vowels involve the tongue during their articulation, meaning that all vowels are [dorsal] by default. Due to the nature of vowels, it is not necessary to include the feature [dorsal] in a description of vowel distinctive features. Instead, vowels can be further specified on where and how high the tongue is during articulation and the roundness of the lips.
Vowel features include [+/-round], [+/-high], [+/- low], [+/- back], and [+/- advanced tongue root] (ATR for short). For a more in depth discussion of each vowel feature, click on the respective term.