When you add an anamorphic attachment with a single-focus unit, it is necessary to secure a taking lens in the infinity focus position.

This lock ring serves this purpose.

It has 2 inner diameters - 58mm and 60.2mm. It was designed for some Helios lenses (a list will be provided later).

Please measure your lens original focus ring diameter and adjacent immovable part diameter to see if the clamp can fit there.