For longer erection and too last longer. Take L-Arginine 4 pills a day, 2 pills in the morning and 2 pills at supper. Take L-Citrulline 2 scoops 45 minutes before a work out empty stomach 1 scoop at night before bed or in the morning, ( I prefer in the morning). I went to ask the best Urologist in Montreal, cost me 180$ a session for those advice, it's not harmful take it on a daily basis.