Zoom gear for Sigma 24-70mm F2.8 DG Lens
https://seafrogs.com.hk/collections/zoom-gears/products/zoom-gear-for-sigma-24-70mm-f2-8-dg
Compatible with 6-inch Flat Long port only
https://seafrogs.com.hk/collections/flat-ports/products/6-inch-flat-long-port-sony-16-35-f28-fe-24-105