SPF stands for Sun Protection Factor, and it indicates the ability to block UVB rays. The concept was pioneered at the Coppertone Solar Research Center in 1972. The numbers themselves stand for the approximate measure of time a person who has applied protection can stay out in the sun without getting burned. Say you get burned after 20 minutes in the sun without protection; if protection is properly applied, SPF 30 protection would allow you to stay in the sun 30 times longer without burning than if you had no protection at all. So, theoretically, you should have approximately 600 minutes, or 10 hours, in the sun. But it’s not an exact science because the amount of UV light that reaches us depends on a number of factors, including cloud cover, the time of day, and the reflection of UV rays off the ground. Royal Tinting’s window films block at least 99% of UVA and UVB, providing among the highest SPF ratings possible.