R9 is a member of the C/D box class of snoRNAs which contain the conserved sequence motifs known as the C box (UGAUGA) and the D box (CUGA).
R9 snoRNAs are part of the C/D box class, which includes other snoRNAs that share similar sequence motifs, such as the C box (UGAUGA) and the D box (CUGA).