What is this? The coupling shaft is made of 45# steel, suitable for connecting servo motor, stepper motor, encoder, screw driving, machine platform, etc. What will I get? The coupling shaft, we provide here, is in size of: Bore Diameter: 22mm to 25mm/0.87 inch to 0.98 inch; Length: 51mm/2.01 inch; Outside Diameter: 44mm/1.73 inch; Slot Width: 6mm/0.24 inch, 8mm/0.31 inch; Thread Size: M6*1M8*1.25; Color: Black In the package of 1 x coupling shaft Are there any advantages of the product? The flexibility of the coupling shaft joint removes stress between the motor and drive components. High hardness, durable, and excellent response, not easy to loosen. What should I notice? All size is measured by manual, please allow +/-0.1 inch error. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Sold by-DIMEANI official store