Feature●Connection Bore Diameter: 8mm to 8mm; Total Size:25x14mm/0.98x0.55(LxD);Thread Diameter: 3mm/0.12".●Widely used in blowers,3D printer,DIY robots,CNC machine,stepper motors,etc. Similar to rigid clamp couplings, shaft couplers are used to hold bearings and sprockets tightly on the shaft, and are used in motor and gearbox assemblies.●Top tight type rigid coupling with 2/4 screws to hold the shaft tightly; high torque with rigidity, low inertia and excellent sensitivity.●NOTE: The rigid type basically does not allow eccentricity, and it must be fully adjusted during use.●Single piece set screw clamp design makes it easy to set up the items on the shaft and control the holding capacity of the coupling.Description -The coupling is great for connect your motor of 8mm to 8mm shaft to the wheel. -Can be used in electric car toy, robot, etc.