Uxcell a13052700ux0220 6mm to 8mm Bore Rigid Copper Motor Coupling Coupler W Tight Screws, Rubber Product name: motor wheel coupling; bore: 6 mm/ 15/64", 8Mm/ 5/16" Overall Size : 16 x 22mm / 0.63" x 0.86"(D*L);Material : Copper Color: gold tone