The Libyco-Berber script is a fairly strict abjad, in which only consonants are written. The principal exception is H, which word-finally seems to mark vowels. The transcriptions used in the principal reference for Libyco-Berber inscriptions, RIL, is as follows:
(source: Chabot, J.-B. 1940. Recueil des Inscriptions Libyques. Paris: Imprimerie Nationale.)
Of these, U and I are better transcribed W and Y, to reflect their consonantal value, while Ç corresponds to Punic ṣ. The phonetic differences between the various Z's and T's are not certain. Some letters' values are not certain, particularly in the Western inscriptions, due to lack of bilingual texts containing them. These include (according to RIL):
Some of these, however, may just be variants of better-known letters.