|Location Map ( geo)|
|From:||Hillhead of Auchreddie (NJ865470)|
|Distance:||4.8 miles (7.7 km)|
|Meets:||B9170, C29S, C26S|
|Route outline (key)|
The C121B starts on the B9170 at Hillhead of Auchreddie to the west of New Deer and heads a little south of west, through Cairnbanno and across the C29S at a crossroads to meet the C26S at Keithen. The western end of the route was formerly the C121S.