It is little known that most sunscreen products provide almost exactly the same level of protection from the Sun. Sun Protection Factor (SPF) refers to the length of time that protection will last. So, if a product that you apply has SPF20, the time limit on its protection once applied is a simple mathematical formula (factor x 10 minutes). SPF50 products protect your skin for the longest period of time: 50 x 10 = 500 minutes of protection (over 8 hours).