SmallRig 1549 Single 15mm rail clamp onto the nato rail, lock with the wingnut. Then attach a 15mm rod into the clamp and use a hex spanner to secure the rod tightly via the side screw.
Rail Clamp Weights of 40g | Aluminum Alloy Construction | Mounted on a Plate / Cage / Handle for Rod Extension | Connect Your DSLR Rigs by Utilizing the Long Hole and Srews
Cold Shoe Mount for Accessories | Mounts to Rigs, Brackets, and Cages | Bending Bevels Prevent Accessory Removal | Arrows for Accessory Directional Mount
12mm Thread Rod Cap | Durable Aluminum Construction | The Rod Cap is Screwed into your Rods | It Prevents Your Equipment From Sliding Off From Your Rods