The SPF rating is a measure of how effective a sunscreen is against UVB which causes skin damage and darkening of your skin (rating range: 1 to 50). The PA system is a measure of how effective a sunscreen is against UVA which slowly damages and ages your skin (rating range: + to +++). This product is rated highest on both measurements. - Rated highest on both SPF and PA measurements. Provides powerful protection against sun damage