Du-Bro 369 - 2-56 Swivel ball Link for 4-40 rod (1)Du Bro Swivel Ball Link 2 56 4 40 with Hardware (1) This high quality ball link offers smooth, secure operation with less slop. You'd want to use this on any control surface where accuracy is required (like the throttle linkage). Includes: 1x swivel ball link (Black plastic, self threading for 4 40 rod, 1" in overall length) with a burnished brass ball pre installed with a #2 hole in it 1x 2 56 x 1 2" socket cap screw 1x brass spacer 1x 2 56 steel nut