The Cokin BP400A Filter Holder for M Series is an lightweight holder and can hold up to 3 filters.
The Cokin BP400A P-series holder allows photographers to attach up to 3 square or rectangular filters depending on the creative effect they are trying to achieve.
The P-series holder will work with Full-Frame lens focal lengths 24mm and greater. If you use the holder on a lens that is wider than 24mm there is a very good chance that you will see the holder in the corners of your pictures, This is also called a vignette or vignetting. It is also possible that you will experience vignetting even at 24mm if the holder is rotated off center axis.