Progressively polish axles to reduce friction for a smooth spin! First, use the triangular file to remove burrs, chamfer and to notch nail-type or one-piece axles. Next, progressively polish with 7 grades of polishing paper - 700 to 2000-grit. Kit includes magnifier to monitor your polishing progress and enough product to polish the axles of five cars. For a final finish equivalent to an 8000-grit polish, follow up with the Diamond Finishing Kit™ (P4039).