Hyaluronic Acid 2% + B5 (Original Formulation) is the original hyaluronic serum from The Ordinary. This rich serum hydrates and gives smoother-looking skin, while working to strengthen the skin barrier. Testing Shows: Replenishes skin hydration Strengthens the skin barrier After 4 weeks: Skin smoothness is enhanced. Elasticity and firmness are boosted.* This formulation contains 4 types of hyaluronic acid and pro-vitamin B5. 4 Types of Hyaluronic Acid: A combination of low-, medium- and high-molecular-weight hyaluronic acid molecules and a next-generation HA crosspolymer support hydration to multiple layers of the skin for a smooth appearance. Pro-vitamin B5 (Panthenol): Supports the formation of essential skin barrier components like ceramides and fatty acids, further improving the skin's moisture retention and an overall healthy appearance.