This plastic hood acts as a lens shade and clips directly on to the Cokin "P" filter holder. It is possible to stack multiple hoods to create a longer lens shade for telephoto lenses.
Attaches to outside of filter holder
Doesn't impede graduated filters' movements
(assuming a 24 x 36mm format 'full-frame' DSLR or 35mm camera...) - Use 1 hood for a 24mm or 28mm lens - Use 2 hoods for 35mm lenses - Use 4 hoods for 50-70mm lenses - Use 5 hoods for lenses 75mm and longer
(assuming a 6 x 6 cm format medium format camera...) - Use 1 hood for a 50mm lens - Use 2 hoods for 70mm lenses - Use 3 hoods for 85mm lenses - Use 4 hoods for 105mm lenses - Use 5 hoods for lenses 135mm and longer