Hi Michael, we're thrilled to hear these steel balls made such a positive impact on your project! The grading of balls relates to their accuracy. Pretty much standard for us is the same as those you purchased which is Grade 25. That designates a ball that has an accuracy in total sphericity and diameter of 25/1,000,000 of an inch. Rolex has nothing on the bearing manufacturers when it comes to accuracy. Thanks for sharing your experience.
