Jym Supplement Science | Jym Pre-Jym (20 Servings) - Rainbow Sherbet Pre-Workout Supplements Supplement Science | The Pre Jym Formula Is Based On Amino Acids (The Building Blocks Of Protein) That Fuel Your Muscles And Provide “Clean Energy. ” The Only Stimulant In Pre Jym Is Caffeine, Selected For Its Performance-Enhancing Benefits, Not Simply To Give You A Jolt. Pre Jym Changed An Entire Sports Nutrition Category When It Launched In 2013. | Jym Pre-Jym (20 Servings) - Rainbow Sherbet