Optimum Nutrition Nitric Oxide is a cellular gas that causes blood vessels to dilate engorging the muscles with blood increasing oxygen amp nutrient delivery & facilitating the removal of metabolic waste products that lead to fatigue. This cascade of events is what rsquo s known as The Pump. Features bull Sustained Release Delivery System Promotes All Day N.O. Activation bull Convenient 3 Tablet Serving Size bull No Caffeine bull Part of the Vassive Size amp Strength Stack Consum