Sunday Riley A+ High Dose Retinoid Serum 15mlProduct Description Advanced strength retinoid serum delivers a 6. 5% solution of stabilized retinoid blends and botanical, retinol alternative extracts into the skin. How It Works Combining 5% retinoid ester blend, 1% liposomal encapsulated retinol blend, and 0. 5% blue green algae with natural, retinoid alternative activity, this serum fights the signs of aging and improves the look of congested and UV damaged skin. Encapsulated CoQ10 helps to