Clamp Coupling 6.35 or 8 to M12 screw

Clamp Type Flexible Coupling

Diameter 25mm, Length 30mm
6.35mm motor shaft to 12mm or 8mm to 12mm leadscrew, ballscrew.

Don't understand why it's known as jaw coupling But it use set screw to clamp the coupling instead of setting onto the stepper motor shaft.
It's one of the cost performance options, set screw type and clamp type, instead of ball screw or rigid coupling for 3D Printer.