Reduce friction and ensure even pressure between the wheel and the scooter bottom

To install:

1. First, take off the old wheel. Using two Allen keys, insert one into the square side of the bolt and hold it steady. Insert the second Allen key into the round side of the bolt and rotate counterclockwise to loosen. Remove the wheel.
2. Remove the screw holding the shank to the scooter.
3. Remove the washer between the shank and scooter bottom.
4. Place the new washer between the shank and scooter bottom.
5. Replace the shank, securing it to the scooter chassis by tightening the screw.
6. Slide the square side of the bolt into the shank so the round side of the bolt points to the outside of the scooter.
7. Slide the wheel onto the bolt.
8. Using two Allen keys, insert one into the square side of the bolt and hold it steady. Insert the second Allen key into the round side of the bolt and rotate clockwise to tighten.