The reason to have both M52x1mm female/ male threads is that you can use easy-to-get universal M52X1mm adapters with this one for your application... Otherwise, with only the Iris Diaphragm itself, you need to find a way to attach it to your lens/adapters, etc... which often times is not easy or at least not elegant :-)
these are high quality item, usually used in camera or projection lenses, can also be used with some mount adapters for adjusting the aperture.
the dimension of the Iris:
Max. aperture diameter: appro 44mm
min. aperture diameter: appro 2mm
the dimension of the outer casing:
outside diameter: appro 71mm
thickness: appro 12.3mm (w/o the male M52 thread); appro 17.3mm (w/ the male M52x1mm thread)
Material for metal,reliable performance.Durable.
one pc adjustable Iris aperture 2-44mm with male / female thread M52x1mm or M42X1MM for camera according to your choose
Other size you can choose ,thankyou!