The Sigma Clamp-On Ring 162mm COR-11 is designed for the Sigma Cine High-Speed 14mm T2 FF prime lens. It attaches to the lens and extends the front diameter to 162mm. When this setup is used with a wide-angle matte box that uses 6.6 x 6.6" square-type filters, vignetting is avoided when shooting with full-frame cameras. The clamp-on ring is also compatible with the Sigma Sf Extender Sf-E1 and other third-party accessories.