Certain Dri Prescription Strength Roll-On is prescription strength, with 12% Aluminum Chloride, and the most effective antiperspirant you can buy without a prescription. Other antiperspirants may have aluminum complexes at higher percentages – but they are not the same. Aluminum Chloride is the strongest and most effective active ingredient available in antiperspirants and is the same active ingredient in many prescription formulations. Aluminum Chloride is the #1 doctor recommended active ingredient for excessive sweating and is why Certain Dri Prescription Strength Roll-On is different from the rest. Directions For Use:  Apply Certain Dri antiperspirant to underarms at bedtime. That’s because the active ingredient works best while you sleep to stop perspiration all day. It will not wash off the next day, even after bathing or showering.  Apply sparingly to completely dry armpit. Apply Certain Dri sparingly – only a few strokes under each arm. To reduce the risk of irritation, be sure underarms are completely dry before applying.  For added deodorant protection, Certain Dri Everyday Strength Clinical antiperspirant + deodorant may also be re-applied in the morning for an extra layer of freshness and protection. Size: 1.20 oz. (35.5mL)