Boost Muscle Pumps, Vascularity and Hardness. 100% Arginine Ethyl Ester HCL. A2 Pump-is an esterified form of arginine (C15 H22 N4 O3 HCl) designed to penetrate the lipid membranes of muscle cells where its unique molecular structure increases nitric oxide production resulting in full, hard, pumped muscles. A2 Pump works at only a fraction of the dosage required with other forms of arginine. The effects of A2 Pump are noticeable within just a few days of use. Increase Muscle Pumps, Increase Vascularity, Increase Muscle Hardness.