Its vowel backness is front, which means the tongue is positioned as far forward as possible in the mouth without creating a constriction that would be classified as a consonant. Note that rounded front vowels are often centralized, which means that they're in fact near-front.
Its roundedness is compressed, which means that the margins of the lips are tense and drawn together in such a way that the inner surfaces are not exposed.
Engstrand, Olle (1999), "Swedish", Handbook of the International Phonetic Association: A Guide to the usage of the International Phonetic Alphabet., Cambridge: Cambridge University Press, p. 140, ISBN0-521-63751-1
Fougeron, Cecile; Smith, Caroline L. (1993), "French", Journal of the International Phonetic Association23 (2): 73–76, doi:10.1017/S0025100300004874
Lass, Roger (2002), "South African English", in Mesthrie, Rajend, Language in South Africa, Cambridge University Press, ISBN9780521791052