HYDROMAX™, high concentration glycerol.
These research studies claim that L-Arginine supplementation may not be the ultimate path to boosting nitric oxide after all:
Q: So if our bodies produce L-Arginine on their own, what can we do to maximize nitric oxide for more muscular endurance and larger pumps at the gym?
A: Inhibit the enzymes that breakdown nitric oxide (AgmaPure™), support L-Arginine synthesis by the body (L-Ornithine HCl) and slow down L-Arginine breakdown (L-Norvaline.) Then to top it off, take the highest concentration glycerol ingredient you can get your hands on (Hydromax™.)