What are yellow Xanax bars? Xanax bars are high-potency bars containing 2 mg and 3 mg of the active ingredient alprazolam, and they are widely available in different colors and strengths. It is prescribed per the signs and etiology of the disease. Yellow Xanax bars come scored “RO39” with three vertical lines for equal dose distribution since they contain 2 mg of Xanax, considered a...