PHL L-Arginine 1000 Capsule contains L-Arginine, an amino acid that stimulates nitric oxide, a short lived compound involved in circulatory and immune function. L-Arginine serves as the precursor for continued nitric oxide production and supports muscle mass & athletic performance. Because of the role that L-Arginine plays in vasodilation, in addition to improved sexual health, it also promotes healthy blood vessels and support vascular health.