These generally come already made-up with diffusion installed.  They are designed to be placed on a C-stand in front of the light to create a large soft source.  Some are flat and some are made of square tubing.  All come with a ⅝” stud for mounting.  We also have some 42″ x 42″ frames that are a nice size: they fit in a van but are bigger than a 3 x 3 ….