Thickness: appro 13mm (w/o the male M42 thread); appro 17mm (w/ the male M42x1mm thread). The reason to have both M42x1mm female/ male threads is that you can use easy-to-get universal M42X1mm 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.
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