cylinder size

So I ordered the Mighty vac back in November. Read a thread about sizing, while I was waiting for it. I realized I should of ordered a different size, so I paid a discounted fee for a new one. They took the money from my checking account, but I never received the new cylinder. As you can imagine...

So I was finally able to find some time to unbox my new Mighty vac this morning. Unfortunately I will not be able to test it out. I definitely ordered one size to big. Could I return it, or do I need to buy another cylinder? Bummed out. :(

I think this warrants a special focus upon. The post will be edited and updated as we go to reflect the inquiries. When selecting a cylinder size, make sure to understand the needs for the setup. At the same time, YOU MUST precondition your penis before going into higher pressure. Do not go...

does the size of cylinder vs penis size make any difference? and also besides the balls getting sucked in obviously. does larger cylinder affect anything when pumping?