Shaft Coupling Range: 6.35mm to 8mm / 0.25 to 0.31 inch
Material: Aluminum alloy with 25mm x 20mm ( L x D ) / 0.98x0.79inch ( L*D )
Provides torque translation and alignment, Cost effective coupling design
Not easy to loosen
Useful in RepRap 3D Printers and small CNC machines