The Hensel Parabolic Umbrella, 32 in. (80cm) has a black backing. It softens, broadens, and diminishes the light output of tungsten or flash light source. A white umbrella without a black backing could also be used as makeshift softbox, Choosing umbrella size is determined by the size of the subject, and the strength of the light supply being used.
The white umbrellas are the right choice for all cases when soft light with soft shadows is needed. For portrait or fashion photography as general light or as fill light - endless uses!