  The cosmic ray energy distributions contain spectral features, that is narrow
energy regions where the slope of the spectrum changes rapidly. The
identification and study of these features is of great importance to understand
the astrophysical mechanisms of acceleration and propagation that form the
spectra. In first approximation a spectral feature in often described as a
discontinuous change in slope, however very valuable information is also
contained in its width, that is the length of the interval in logarithm of
energy where the change in spectral index develops. In this work we discuss the
best way to define and parametrize the width a spectral feature, and for
illustration discuss some of the most prominent known structures.
