This award-winning serum captures the most gentle and effective form retinol on Earth (retinal)––estimated by dermatologists to be 20x more effective than regular retinol. This elusive ingredient is captured using Protocol's patented oxygen-free bottling technology, designed by the Protocol Lab Team in collaboration with aerospace engineers. Most clients see improvements within 10 days. Key Active: 0.1% retinal, the enzyme-calibrated form of retinol. (i.e., naturally-occuring retinaldehyde) (Estimated 20x more effective than regular retinol) 30ml/1fl oz A retinoid that's 20x more effective than regular retinol...and without the drying