The usual explanation of the cardinal vowel system implies that the competent user can reliably distinguish between sixteen Primary and Secondary vowels plus a small number of central vowels. The provision of diacritics by the International Phonetic Association further implies that intermediate values may also be reliably recognized, so that a phonetician might be able to produce and recognize not only a close-mid front unrounded vowel [e] and an open-mid front unrounded vowel [ɛ] but also a mid front unrounded vowel [e̞], a centralized mid front unrounded vowel [ë], and so on. This suggests a range of vowels nearer to forty or fifty than to twenty in number.