The role of this ring is replaced, the objective of the SLR camera with this ring. This then allows, thanks to its release 'standard' to adapt many kinds of devices (magnifiers, microscoped, lunetted astronomiqued, some older lenses, etc.) As for me, I connect my camera to a trinocular microscope to take pictures of objects that I studied. This adapter perfectly fulfills its function, and build quality is excellent (it's heavy! Steps from the small plastic). Moreover, the price seems very reasonable to me.
