These stainless copper shaft couplers allow you to couple the different size shafts together. They can be used for connecting motor shafts to drive shafts, or two different sized shafts. The strength of the copper coupler is higher than aluminum coupler, Suitable for the bigger size shaft , All of they come with a hex wrench.Specification: Length: 22mm Diameter: 15.7mm Bore: 6-10mm Weight: 25.0g