C-SunGuard SPF 30 is a daily sunscreen providing broad-spectrum sun protection for healthy skin. This ultra-sheer Z-Cote formula helps prevent sunburn from UVB radiation and protects against long-UVA rays linked to deep premature skin-aging of the skin, while simultaneously protecting the skin's Photolumines quality. Apply each morning and liberally during the day as part of the Obagi-C Rx System.