In this era of evidence-based medicine, you are supposed to consider evidences, pure facts and real testimonials, not claims. Pro Extender Accordingly, go for a penis extender that is clinically backed by a number of trials and studies and has been recommended by full-fledged health experts and doctors. A good penis extender, therefore, should be clinically proven not only to enlarge your member but also improve overall sexual performance and pleasure. One of the best ways to check credibility is to see whether the product has been recommended by full-fledged medical practitioners and certified health care providers.