Z18 snoRNA belongs to the C/D box class of snoRNAs which contain the conserved sequence motifs known as the C box (UGAUGA) and the D box (CUGA).
The Z18 snoRNA is a type of small nucleolar RNA (snoRNA) that falls under the C/D box category, distinguished by its possession of the conserved sequence motifs C box (UGAUGA) and D box (CUGA), which are also found in other snoRNAs.