Neutrogena Hydro Boost products contain various concentrations of hyaluronic acid, depending on the specific product. The Hydro Boost Water Gel, for example, contains 1.5% hyaluronic acid, while the Hydro Boost Gel-Cream has 3% hyaluronic acid. It's worth noting that the concentration of hyaluronic acid is just one factor to consider when evaluating a product's effectiveness, as the overall formulation and other ingredients also play a role in its performance on the skin.