ISDIN Si-Nails is a professional nail strengthening treatment that contains cationic hyaluronic acid to protect and improve nail appearance. This click-pen applicator delivers a formula that helps increase nail thickness, density and durability while moisturizing cuticles, with visible results in as little as 14 days. Before first use, activate the click pen by pressing the button 25 times until the applicator is moistened. The product should be applied directly to clean, bare nails and should not be used over nail polish or gel. Results vary depending on initial nail condition but typically improve with extended use. The treatment works by strengthening brittle nails and improving their natural appearance, making them harder, more hydrated and less prone to breakage over the 28-day recommended treatment period.