Rain-X Car Windshield Repair Kit helps you minimize the appearance and stop the spread of chips and cracks in your windshield, helping you save time and money, avoiding a full windshield replacement. Rain-X Windshield Repair Kit is easy to use, and only takes minutes to apply. It removes air from the break, fills it with durable resin and makes it even stronger than before. For best results, repairs should be made as soon as possible after the damage occurs and before the break is contaminated by dirt or water. In addition, avoid the use of glass treatments after the crack has formed and prior to repair. However, glass treatments can be applied one (1) week after repair. The kit works best on round damage not more than one inch in diameter, and cracks not longer than 12 inches. It will not repair damage to more than one layer of glass. Pro-tip to avoid poor results - refrain from applying resin too quickly, air pockets forming during the application or repairing a contaminated crack as this may compromise your results.