NutraBio PRE Stim-Free, as the name implies, is our stimulant free version of our PRE formula. We created PRE Stim-Free for those individuals who are sensitive to ingredients such as caffeine, hit the gym late at night, or otherwise want a pre-workout with the performance boosting ingredients found in PRE minus the stimulants. To that extent we can say PRE Stim-Free is absolutely the most thorough, effective, and purest stimulant free pre-workout in existence. PRE Stim-Free is built upon clinically dosed and scientifically backed ingredients proven to maximize workout performance and produce results. Athletes of all levels realize that in order to achieve the most effective training session that strength, endurance, energy production, and focus are a must. A complete stimulant free pre-workout supplement should support all of these benefits. The synergistic combination of ingredients found in PRE Stim-Free help prepare your body physiologically and psychologically by supporting increases in muscular strength, power, and endurance, enhancing the mind-muscle connection, and combatting fatigue. From top to bottom PRE Stim-Free will help keep you training stronger and longer.