B–C also uses single versus double vowels letters to represent certain short + high versus long + low final vowels even in open syllables where the contrast does not exist: buk, buut, baa, and different letters to represent the contrast in other cases: sek, sin.
The Cantonese high and low pitch registers are indicated by inserting -h- or -r- after the initial: bhat, brat.
Medium pitch register has no insert, and is considered the basic form: baa.
Before the vowel of the final, h indicates that the start of the tone is high; after the vowel of the final, h indicates that the tone falls, however a falling contour is also indicated by a change in spelling in some finals: Vi > Vy, Vu > Vw, ng > nq, n > nn, m > mm for example saan "disperse" and shaann "mountain", sou "number" and show "whiskers", sai "small" and shay "west".
High-register syllables that end in a stop (entering tone) are already considered high-flat and cannot take x.