Replace the carbon brush every 60 hours to prevent overheating of the electric rotating tool. Carbon brush compatible with DREMEL 4000, 90930-04, 2615298790, 595, 395, 300, 6000, 215, 217, 100. Installation instructions: Step 1: Use a wrench to open the carbon brush cover. Step 2: Remove the old carbon brush. Step 3: Install a new carbon brush. Step 4: Secure the cover tightly using a wrench. Note: Replace these brushes every 60 hours. Color: As shown in photo Material: Carbon + metal Package Contents: 6 x Carbon Brushes Due to monitor display differences, actual color may vary slightly from images. Lighting and screen settings may cause slight color differences between the product and the image. Measurement may vary by 1-3 cm due to manual measurement. Package includes only the items listed above; other accessories are not included.