  The rapid development of DNA storage has brought the deletion and insertion
channel, once again, to the front line of research. When the number of
deletions is equal to the number of insertions, the Fixed Length Levenshtein
(FLL) metric is the right measure for the distance between two words of the
same length. The size of a ball is one of the most fundamental parameters in
any metric. The size of the ball with radius one in the FLL metric depends on
the number of runs and the length of the alternating segments of the given
word. In this work, we find the minimum, maximum, and average size of a ball
with radius one, in the FLL metric. The related minimum and maximum sizes of a
maximal anticode with diameter one are also calculated.
