• Front side - M77x0.75 female thread
• Rear side - 92mm inner diameter
• Machined of high quality aluminium alloy

This adapter allows using standard screw-in 77mm filters on Mir-20 (Mir-20M, Mir-20H) lenses with 92mm outer diameter.

Take note that this adapter is for OLD Soviet lenses. New Russian lenses have same name but smaller size, and they need a 75mm clamp instead of this 92mm one.

Also, you should understand that such an adapter introduce vignetting since a filter size is smaller than the lens front glass diameter (see the last photo made with a full-frame Sony A4R IV camera).