Neewer Blue Rod End Protective Cap M12 Thread Stopper Screw for Customized Film Maker System 15mm Rod Support Dslr Rig Rail Clamp(2 pcs Pack) M12 male thread Rod Cap for 15mm Rod Rod Cap M12 Thread Prevent From Accidental Sliding Made of Aluminum Alloy M12(12mm) threaded The rod cap is M12(12mm) threaded and screws into your rods to prevent your equipment from accidentally sliding off of your rods.