I have a RedRock matte box and I know it will hold either a 4x4 or 4x5.56 filter.
I do know that the 4x4 is considered a 100mm square filter when some companys display their filter sizes in millimeters.
So is 150mm the 5.56 size or not? I have been seeing 100mmx150mm and im not sure if it will work on my Redrock Matte Box.
I could settle for the 4x4 but I wanted to try and use the 4x5.56 in case of wide angle vignetting.