Bicycle hub axle jam lock nut (can also be used as a 4mm spacer if your hub spacing is different than your frame or fork spacing)   * Quantity: PACK OF 10 * Threading: 3/8" X 26 threads per inch (usually used on Asian made hubs, particularly freewheel rear hubs and most front wheels. Typically these will not fit coaster brake rear hubs). * Thickness: 4mm * Uses a 17mm cone wrench * Material: STEEL