Only three buses are on 21 (985, 986, 987).
980 is with HGDEP on 107, while 981 & 982 are also Hougang
buses but SPs. 983 is ex-HGDEP with 9, but got transferred to Bedok
after 9's fleet all got transferred. 984 is HGDEP 153 while 988
& 989 are BNDEP 15 buses.