Extenze is one of the top three herbal supplements tested. Results were average and there are few positive effects, however many people do claim an increase in length. Extenze has Yohimbe in their formula. Yohimbee has been known to cause high blood pressure and serious damage to the liver. We highly recommend that you avoid any product that has Yohimbe in its formula especially if you have heart or liver problems. Extenze has a 2-month satisfaction guarantee. The customer satisfaction is about average.