These 3/4"-20 thread axle nuts fit 500 / 650 c.c. Triumph motorcycles rear axle / spindle. This is the 'thin' axle nut, a thicker style was also used on the brake plate side and on each end of the axle. Stock application there would have been one of these on the right side (as if seated on bike) of the speedometer, which is to the right of the rear hub. Brand new, zinc plated. Stock part number is 37-1282.