This is LEE 100mm soft graduated Neutral Density filters.

These filters allow the transition to be blended into the scene. A neutral density 0.6-to-clear, with a two stop differential, will generally compensate the average bright sky-to-foreground situation. LEE graduated resin filters are 4"×6" (100mm×150mm)×2mm thick. The 6" length allows for adjustment of the filter within the holder. Inculded in a soft pouch,