The Schneider 5.65x5.65" Combo Graduated Neutral Density 0.6-1.2 Glass filter is an interesting variation on traditional graduated ND filters.
Half of this filter is a standard 1-stop Neutral Density (ND0.3) filter that transmits 50% of the incoming light while the remaining half of the filter is a graduated Neutral Density 0.6-1.2. In simpler terms, it is basically a solid ND filter combined with a graduated ND.
Often it is necessary or desirable to balance the light intensity in one part of a scene with another. This is especially true in situations where you don't have total light control, as in bright contrasty landscapes. Exposing for the foreground will produce a washed-out, over-exposed sky while exposing for the sky will leave the foreground dark and under-exposed. This filter enables cloud detail to be kept correctly exposed in the picture while "tweaking" the lower half of your image.
Determining which graduated neutral density filter yields ideal results for any given lighting situation takes knowledge, experience and a collection of such filters. Choose the filter strength which adjusts the lighting to stay within the exposure latitude (greatest difference between bright/dark values) which still shows details in both of the digital or film medium in use.
The Soft or Hard label indicates the degree of color graduation. Horizontal/Vertical indicates the direction of the graduation.