My husband uses them. They increase his size while he's using them but it seems like as soon as he's done with it he goes right back to the size he once was. Basically, it increases the blood supply in your shaft and temporarily engorges your penis. They can have scary side effects such as:* Hemorrhagic spots on the penis (petechiae)* Numbness or coldness of the penis* Pain or bruising of the penis* A sense of trapped semen during ejaculation or delayed ejaculationHere's an article from the Mayo Clinic: link"Although penis pumps are a safe erectile dysfunction treatment for most men, if you have certain health problems such as blood coagulation problems or sickle cell anemia, or you take certain medications such as blood thinners, you need to be more cautious when using this method. Talk to your doctor about your health conditions and any medications you're taking to make sure you are getting the safest and most effective erectile dysfunction treatment." less