The railblock Rod Clamp can be mounted on any standard 15mm rods on DSLR Rig. * Precision CNC machined from aluminum. * Rails center-to-center distance : 60mm. * And there are 4 types of Thread: 1/4", 3/8", M4 & M5 thread, which are very useful if you like to DIY DSLR Rig * Ratchetting knobs,Adjustable Levers,Metal M5 thread Knob Screw.