Over 80% of replacements per year are caused by edge cracks, with impact points less than three inches from the edge.

1. A Defect around the perimeter of the glass due to the thermal effect of the manufacturing process.

2. Induced stress (the second defect) from the windshield being glued to the vehicle, which also aggravates the weak spot. (Defect)

3. Tension fields created by the weak spot, mechanical stress and temperature variance.

4. Fracture mechanics, where critical size and fracture force decreases as you approach the edge.

5. Theory of Elasticity, where tension stresses are produced around the perimeter from inside versus outside temperature variations.