The Dual-Lock coupler has two set screws with locking nuts offset 90 degrees from each other. This dual set screw design draws up the connection thereby eliminating the potential of undesirable lost motion with normal spline clearance. To prevent spline deformation the locking screws are positioned to locate in the external retaining groove of the pinion. The splines in these couplers are precision broached to the correct size and we guarantee they will fit their intended purpose.