Irwin steel-libido red is specially designed to support Nitric Oxide in the body. It features the Nitric Oxide “booster” L-Citrulline – an amino acid that supports blood circulation and enhances physical response during sexual activity. When it comes to sexual performance, Nitric Oxide is the key! Nitric Oxide is a naturally-occurring compound in the body that plays a critical role in the male sexual response.* Nitric Oxide is produced in the inner lining of the vascular system and helps to dilate blood vessels, allowing blood flow to vital organs. When sufficient Nitric Oxide is present, erections occur during the normal course of intimacy.