Replace it every 60 hours, otherwise the electric rotating will overheat.Carbon brush, suitable for carbon brush, used for electric knife sharpening 3000,200.Application: Suitable for 3000, 200.installation :Step 1: Use a wrench to open the carbon brush cover.Step 2: Take out the carbon brush.Step 3: Replace the carbon brush with a new one.Step 4: Use a wrench to lock the lid firmly.Note: These brushes should be replaced every 60 hours.Size: about 48x48x10mmMaterial:Carbon + metalcolour:As shownPackage Contents:10 x Carbon BrushesOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.