5 - 8 mm Coupler is discontinued now. We recommend you Robot Parts as an alternative where you might find other products interested.
This is a 5mm (0.2") to 8mm (0.31") Aluminum coupler. A common application for this coupler is to connect a stepper motor with a 5mm (0.2") axis to a larger 8mm (0.31") rod. In 3D printers it is commonly used to opperate a threaded rod.
This coupler is cut like a spring, giving it a flexible and spring property.