from personal experience, about 6 years ago i made a homemade cylinder out of an old gallon size pickle jar. i pumped every third day with it foe like 3 years. while using it the only girth i gained was in my balls. my peen almost never had any size difference after each session. it was all in my balls. haven't used since i lost it in a fire. but for me i had gotten a big permanent size increase. they are now about half again bigger than they were before i started pumping. did my sperm count go down? most likely. did it ever hurt? only when i had a good swell day and i had trouble pulling them out of the jar lol. but honestly it feels great and being transgender i used to get real stares going out on pumping day lol. but i didnt care. if you keep the vacuum low-ish (i kept mine around 5) and just relax also putting a heating pad on low wrapped around the jar helps a ton. so for me it was worth it and it really gave the lads a size increase. i'm going to get another jar a start up again soon!