Rigid couplings will keep backlash to a minimum, since the coupling is one single piece. Generally, the motor shaft with a 1/4" diameter will be inserted in one end, and a shaft, or lead screw also measuring 1/4" in diameter will be inserted into the other end. The screws that clamp the shafts will be tightened, but not too much. These types of clamping couplings will not damage the shafts.
This coupling is called a clamping coupling or clamp coupling. The length of this rigid coupling is 1.129 inches (28.7 mm). The diameter is 0.743 inches (18.87 mm). The tool needed to tighten the coupling is a hex key or allen wrench (not included) with a size of 3/32 inches. There are four screws in total, two for each shaft that is inserted into this coupling.