The time that *"z", a voiced apical alveolar fricative, represented in runic writing by the algiz rune, changed to "ʀ", an apical post-alveolar approximant, is debated. If the general Proto-Norse principle of devoicing of consonants in final position is taken into account, *"z", if retained, would have been devoiced to and would be spelled as such in runes. There is, however, no trace of that in the Elder Futhark runic inscriptions, so it can be safely assumed that the quality of this consonant must have changed before the devoicing, or the phoneme would not have been marked with a rune different from the sowilō rune used for "s". The quality of the consonant can be conjectured, and the general opinion is that it was something between and , the Old Norse reflex of the sound. In Old Swedish, the phonemic distinction between "r" and "ʀ" was retained into the 11th century, as shown by the numerous runestones from Sweden from then.