I have a few different types of Penis Pumps and have been pumping for almost 12 years now. First, they do work....LoL You will immediately notice an increase in thickness and with a pumping regiment you will notice some increase in length. Be sure to look for a penis pumping blog or website to get started. Never pump with a great deal of pressure, it should never hurt. Low pressure and long sessions work the best, along with some sort of heat, say a hot bath or a heating pad. I have gained as much as 2" in thickness and an inch in length. That is not to mention the 2 stage pumps that work on your cock and balls at the same time. My sac has gotten to over 16" around. On average the effects will last anywhere from 3 days to a week or more. Please don't buy the cheap pump sets, do your research and get something worth while! Feel free to ask any other questions! My wife and I love to pump together!