Camera Accessories
15mm Rod Clamp Rail Block Compatible with 1/4-20 & 3/8-16 Thread Hole DSLR Camera Cage and Shoulder Rig
Four standard 15mm rod holes (60mm center to center distance Arm Connection, 4 Hole Adapter Rod Clamp Two 15mm double rod clamps, extension accessories Aluminum alloy, lightweight for long time use Has 1/4-20 & 3/8-16 mounting holes
https://www.bizrate.co.uk/cameraaccessories/15mm-rod-clamp-rail-block-oid40342785951.html