  Let $D_n$ denote the $n$-punctured disk in the complex plane, where the
punctures are on the real axis. An $n$-braid $\alpha$ is said to be
\emph{reducible} if there exists an essential curve system $\C$ in $D_n$,
called a \emph{reduction system} of $\alpha$, such that $\alpha*\C=\C$ where
$\alpha*\C$ denotes the action of the braid $\alpha$ on the curve system $\C$.
A curve system $\C$ in $D_n$ is said to be \emph{standard} if each of its
components is isotopic to a round circle centered at the real axis.
  In this paper, we study the characteristics of the braids sending a curve
system to a standard curve system, and then the characteristics of the
conjugacy classes of reducible braids. For an essential curve system $\C$ in
$D_n$, we define the \emph{standardizer} of $\C$ as $\St(\C)=\{P\in
B_n^+:P*\C{is standard}\}$ and show that $\St(\C)$ is a sublattice of $B_n^+$.
In particular, there exists a unique minimal element in $\St(\C)$. Exploiting
the minimal elements of standardizers together with canonical reduction systems
of reducible braids, we define the outermost component of reducible braids, and
then show that, for the reducible braids whose outermost component is simpler
than the whole braid (including split braids), each element of its ultra summit
set has a standard reduction system. This implies that, for such braids,
finding a reduction system is as easy as finding a single element of the ultra
summit set.
