NeewerAluminum Alloy Z-Shape Offset Raised Rail Block Ajustable Levers for 15mm Rods on DSLR Camera Shoulder Rig The Z shape railclock is used to connecting the shoulder support It is made of Aluminum alloy,very solid Compatible with all 15mm rod support systems 60mm center to center distance system enable more space The locking knob can tighten easily and safely