Presto has introduced a new line of strings for fractional sized double basses: the Balance Fractional (Green Label) strings.
The Balance Fractional strings  have a low tension and small diameters, so they are easy to play even for children. They have a steel rope core, wrapped with tungsten and chromesteel.
Presto Balance Fractional strings are now available in 1/4, 1/8 string lengths (1/2 and 1/10 will follow soon).