Dayton Superior D32 Closed Coupler is available with coil threads for use with D1 and D18 Inside Tie Rods or B12 Coil Rod. The coil threads have been tapped from each end of the coupler providing a positive stop at the center of the coupler. In order to develop the rated load, the inside tie rods or coil rods must be threaded into the coupler until they reach the stop.