The SPF (Sun Protection Factor) on a bottle of sunscreen indicates the level of protection we're getting from the sun's UVB rays—which are the sun rays most commonly responsible for sunburns and skin cancer. SPF 70 blocks 98.5% of UVB rays.
SPF 70 sunscreen is what we reach for when the sun is blazing, the waves are calling, and our skin needs all the backup it can get.