1. remove the retaining ring by turning it counterclockwise, in the direction of the arrow, as shown in the illustration.
2. remove the ball.
3. inspect the ball for contaminants. wipe it clean with a dry, lint-free cloth.
4. if the ball is dirty, wash it in warm, soapy water. rinse and wipe the ball with a lint-free cloth until dry.
5. inspect the ball cavity in the mouse for foreign materials. if there are any foreign materials, remove them.
6. replace the ball.
7. replace the retaining ring on the mouse and align it with the open slots in the ball cavity.
8. turn the retaining ring clockwise until the open slots are covered and you hear the ring snap into place.