These ball linkages are for 6-32 hardware. The brass ball has a 0.14” thru-hole to allow a 6-32 screw or threaded rod to slip through while the nylon body has a 0.1” diameter blind hole which a 6-32 screw will form threads the first time a screw or rod is inserted. The included cups increase the usable range of motion by distancing the ball and the head of the screw used to fasten the linkage to a surface.