These stainless Aluminum 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. All of they come with a hex wrench. Specification: Length: 25mm Diameter: 14mm Bore: 4-6mm Weight: 9.1g Part List： 1 x Aluminum shaft couplers 4 x Net 1 x Allen driver