What size pump cylinder do I need?
This one is for everyone with the pump page open in one tab and a ruler in the other. Cylinder size is the question we hear most before a first order - and getting it right is simpler than it looks. Here is how fit actually works, what your body will tell you, and how to buy once instead of twice.
How should a pump cylinder actually fit?
Snug but comfortable. The opening should sit flat against your body and form a seal around your growth without pinching or pulling in the surrounding tissue. When the seal is right, a gentle pump creates suction you can feel evenly - a soft fullness, not a sting at the rim. Our cylinders are custom-molded for bottom growth anatomy rather than repurposed from nipple pumps, and that shape is most of why the seal works: it was molded for the body it is meeting.
What happens if the cylinder is too big or too small?
Too big, and the cylinder pulls in surrounding tissue instead of focusing suction where you want it - the seal breaks, and the session feels like not much of anything. Too small, and you get pinching at the rim and pressure that concentrates too fast. Either way, your body tells you quickly, and the fix is the same in both directions: change the cylinder, not the effort. Pumping harder never fixes a bad fit. And the non-negotiable: pain, numbness, or color change means release the pressure and stop for the day.
Should I size up as my growth changes?
Many people do, and that is the point of graduated sizes. Start with the smallest cylinder that fits without pinching, then move up when snug turns into crowded. The Deluxe includes three graduated, translucent cylinders for exactly this reason - you can see what is happening in real time and grow into the next size without buying a new pump. If you like tracking, the included measuring stickers pair well with our guide on how to measure bottom growth.
Which pump should I buy if I am not sure about size?
The honest matrix: the Pump 2.0 comes with one custom-molded cylinder and is the simplest start. The Deluxe is the same manual pump with three graduated sizes, so you are never boxed in - the pick if you are between sizes or expect to grow. The Pro Pump also includes three sizes and adds a digital gauge, for precise, repeatable sessions. For the full side-by-side, read our Pump 2.0 vs Deluxe vs Pro comparison, and if you want your pump paired with more, the pump kits bundle it with gear built to work together.
Real talk: nobody feels certain about sizing before their first pump - you are not behind, and you are not the exception. Bodies vary, growth varies, and that is exactly why we mold multiple sizes instead of pretending one fits all. Order the setup that gives you room to find your fit, start gentle, and let your body lead. You do not have to get it perfect on day one. You just have to start where you are.
Frequently asked questions
Which cylinder size should I start with?
Start snug but comfortable - a good seal matters more than size. Most people begin with the smallest cylinder that fits without pinching, then move up as their body responds.
How do I know if my cylinder is too small?
Pinching at the rim, discomfort at the base, or pressure that builds too fast. Move up a size - more effort never fixes a bad fit.
How much pressure should I use?
Start gentle - soft fullness, never pain, numbness, or color change. A few light squeezes is plenty at first, and early sessions of 5-10 minutes are enough.
Do I need to be on T to pump?
No. Pre-T, post-T, or never on T - cylinder fit matters more than where you are on your journey.
What is the difference between the Deluxe and the 2.0?
Same manual pump, different range: the 2.0 includes one custom-molded cylinder, the Deluxe includes three graduated sizes so you can size up without buying again.
Why trust us: we have been designing gender-affirming gear since 2012 - 14 years of molding products for our bodies, because we are the community we make for. Questions about fit? Join our office hours, Wednesdays at 9pm ET, and ask us anything.
You already know which one you are leaning toward. Find your fit in the trans masc pump collection.
This article is for education and encouragement, not medical advice. If you have questions about pumping and your health, check in with a provider who gets it.
