This set consists of a Graduated Mist, a Mist Stripe and a Mist Clear Centre Spot.
These filters can be used individually or in combinations to create varying densities of mist and fog. 
The stripe can often be used to cover the foreground of the shot, providing a feeling of depth of fog, while the clear centre allows the viewers eye to be taken straight to the all important subject.
The flexibility of positioning offered by the Lee Filter Holder System significantly increases the choice of effects available to the photographer.