Road film, oil, tar, grease, water spots and more bonds to glass and are difficult to remove. Windshields and especially the rear window on trucks and SUVs are exposed to harsh conditions. Eliminate heavy road film, tar, bug jerky and even water spots quickly and easily. Glass cleaning clay is the perfect glass prep before polishing. Clay also works on a variety of smooth, hard surfaces such as glass shower doors, chrome, stone, ceramic tiles, synthetic stone and quartz surfaces. Removes water spots from windows around your home. Always use a proper lubricant when cleaning with clay. Griot's Garage recommend Speed Shine as a lubricant and micro fiber Speed Shine cloths. 3.5 ounce, 100 gram bar. Finish up with Griot's Garage window cleaner and micro fiber window cloths.