This is a ring-type tripod mount for the FE 70-200mm f/4G OSS lens. It has an inner diameter of φ72 and fits perfectly on the ttartisan 100mm f2.8 t&s lens body, which I used a few times for macro photography. It was convenient for shooting because it eliminated shifts in composition. I am also selling this along with the lens. The bottom is Arca-Swiss compatible, allowing it to be attached to an Arca-Swiss style ball head. It retails for around 4000 yen on Amazon. Project Type: Lens Mount Ring Material: Aluminum Alloy Color: White For Sony FE 70-200 mm f/4 G OSS (SEL 70200 G) lens Quantity: 1 piece Camera Screw: 1/4 inch Weight: Approx. 143 g Round Width: Approx. 18 mm / 0.71 inch Inner Diameter: Approx. 72 mm / 2.83 inch Round Thickness: Approx. 4 mm / 0.16 inch