The screw on type , Hi guys delving into an area I have'nt tried before, First up I dont want an ND 400/9stop , A little less to get some water movement shots around 1 to 2 secs at 8 to 9am in the morning also to play with slower shutter speeds of Surfing and waves , Anybody got any ideas on what strength to get , I was guessing 4 or 5 stops may do the trick , We will be using this with the normal ND grad filters as well , I was thinking this which is 4 stops or the X 32 which is 5 stops , Would these work do you think ?