When people talk about bongs, they usually obsess over the size, shape, or how many percs it has.
Meanwhile, the part that actually gets smoke into the water which is known as a downstem sits there doing all the work and catching none of the credit. It’s the piece that defines how your bong pulls, how smooth your hit is, and whether your filtration setup works or fails.
I’ve spent over a decade designing and testing glass, and I can tell you this: a well-made downstem will change how you feel about your bong.
This guide breaks down the different types of downstems, their materials, sizing, airflow characteristics, and how to make them fit with your current setup without turning it into a frustrating puzzle.
If you’ve ever wondered why one bong hits like a dream while another feels like sipping smoke through a clogged straw, this article will clear that up. Let’s figure out which downstem is right for you.
What Is a Bong Downstem & Why It’s the Heart of Your Hit
A downstem is the tube that connects the bowl to the water in your bong. Simple in shape, but it decides whether your session feels smooth or like you're inhaling hot gravel.
It pulls the smoke down from the bowl and forces it through the water before it reaches your lungs. That movement isn’t just for looks, it’s what cools the smoke, filters out particulates, and softens the hit.
If your downstem isn’t working right, everything else in your setup becomes a wasted effort.
Most people assume the bowl or the percolator handles the heavy lifting. That’s backwards.
The airflow starts with the downstem, and how it’s cut, how long it is, and how it’s shaped will control how much air moves and how much resistance you feel when you inhale.
Whether you're using a single hole, slits, or a more complex diffuser, the stem defines your draw. Ignore this piece and you’ll never get consistent results. Dial it in, and even a basic bong will outperform overpriced setups with bad internals.
Anatomy of a Downstem: Materials, Sizes & Compatibility
A downstem might look like a simple tube, but it’s got more variables than most people expect.
Material, joint size, angle, length, even the shape of the cuts at the bottom are among the factors that affect how your bong performs. Get any one of them wrong and you’re left wondering why your expensive piece pulls like a clogged snorkel.
This next section breaks it all down so you can choose a stem that fits right, hits clean, and actually improves your session instead of holding it back.
Glass vs. Silicone vs. Titanium
Glass is the standard because it looks clean, feels right in the hand, and doesn’t alter flavor. The tradeoff is durability. If it hits a hard surface, it’s done.
Silicone is flexible and won’t shatter, but it sacrifices rigidity and doesn’t hold up to high-heat use. It’s more of a backup than a mainstay. Titanium is the tank of the group. It’s light, strong, and shrugs off heat like it doesn’t care.
People ask if titanium is worth it if you're clumsy. If you've broken a downstem more than once, it's not a luxury. It’s a fix.
Sizing 101: 10mm, 14mm, 18mm Joints
Downstem joints come in three standard sizes. A 10mm is tiny. A 14mm fits a pencil snugly. An 18mm swallows it with room to spare.
You can also use a dime. If it drops into the joint, it’s likely an 18.
If it sits on the rim, you’re looking at a 14. Knowing this up front saves you from buying parts that don’t match.
Joint Gender: Male or Female
A male joint fits into a female one. That’s the rule. If your bong has a wide opening, it’s female, and you need a male downstem.
If the joint sticks out, it’s male, and you’ll need a female stem. Some setups need adapters to bridge mismatches. That works, but it adds complexity.
Stacking too many adapters also affects airflow, and not in a good way.
Length & Angle: Getting the Fit Right
Your downstem should sit just under the water line. If it’s too short, your smoke won’t filter. Too long, and it may clog or hit the base.
Stick a pencil into your bong’s joint and mark where it touches right above the base. Measure that length from the bottom of the ground glass to the tip. That’s the length you want.
Angles matter too. Some bongs have a 45 degree joint. Others sit at a flat 90.
If you force the wrong angle, the bowl won't sit level and the stem won’t seal right. One user measured by eye and ended up with a stem that hovered in dry air. It didn’t touch the water and didn’t filter anything.
The 6 Main Downstem Types
Some downstems are designed for ease. Others chase maximum diffusion. Some prioritize airflow, while a few just want to look wild and do something different.
No two types hit quite the same, and if you’ve only used whatever came stock with your bong, there’s a good chance you’ve never actually felt what your piece is capable of.
Here’s a breakdown of the six most useful downstem styles and where each one shines—or falls short.
Open-End Downstems
This is the most straightforward design you’ll find. It’s a hollow tube with no cuts, no holes, and no intention of breaking smoke into smaller bubbles.
The smoke shoots straight through into the water and back up to you. It doesn’t filter much, but what you lose in percolation you gain in airflow.
If you care more about flavor than filtration, or if you just want something that won’t clog after a long session, this is the one. It’s also ideal for smaller rigs or micro bongs where space is tight and over-engineering gets in the way.
Think of it as the least amount of glass between you and your draw.
Slitted Downstems
Add a few horizontal slits at the bottom of a tube and you get one of the most reliable percolation upgrades out there. These slits force the smoke to break into smaller streams before it hits the water.
The result is smoother pulls and a noticeably softer feel on the throat and lungs.
TAG's slitted downstems are built with precision spacing that creates a signature "purring" sound when you draw—clean, smooth, and satisfying.
This type hits the sweet spot for most users. It's easy to clean, improves diffusion without killing airflow, and makes even a budget bong feel more refined.
Showerhead Downstems
A showerhead stem takes the idea of slits and refines it further.
The bottom end is flared or rounded, and vertical cuts are made in a circle around the perimeter. This lets the smoke diffuse in all directions, hitting more water from more angles.
If you're after denser bubbles and a cooler hit, this is where it starts to get serious. TAG’s Super Slit Showerhead downstems take this to the next level. The cut pattern is engineered to deliver maximum bubble formation with minimal drag.
You get thick clouds and a hit that feels cooled without being choked. For people upgrading from a stock stem, this is often the first major leap in function.
Tree Perc Downstems
This style is basically a mini-percolator built into your downstem. It features several small arms (usually 4 to 9) each with their own slits.
When done right, it splits the smoke into multiple filtered streams, giving you one of the most complete levels of percolation before hitting a second chamber.
The flip side? Cleaning. These can be a nightmare if you let buildup settle in.
A soak-and-shake routine with ISO and coarse salt works, but boiling water is a risk. Thin glass arms can crack under sudden temperature swings.
That’s why some people use this style in higher-end setups but keep a simpler stem on hand for daily use.
Matrix & Honeycomb Styles
These are the tech-forward stems that try to pack as much filtration as possible into a small space. Matrix styles use stacked, grid-cut holes.
Honeycomb stems punch dozens of micro-holes across a flat disc or embedded section. The result is intense diffusion and a very smooth draw.
The tradeoff is drag. If the holes are too small or too tightly packed, it slows your pull and mutes the experience. Some people wonder if this level of diffusion kills flavor.
The answer depends on your material. For low-temp dabs or finely cured flower, yes, you may lose some aroma. For harsh or dry hits, these styles can be a lifesaver.
Multiplying Rod & 5-Arm Styles
These are specialty designs you’ll typically only find from brands like TAG. A multiplying rod stem uses dozens of micro slits arranged on a rod within the main stem.
The 5-arm style functions like a compact version of a tree perc, giving strong diffusion without eating up space.
They’re built for filtration fanatics. If you’re looking for thick, cool rips with minimal splash and want something that feels engineered, these are it.
They pair well with larger bongs, dab rigs, or people who take their sessions seriously. TAG’s CAD-modeled versions offer consistency most brands just can’t match.
Fixed vs. Removable Downstems?
Some bongs come with a fixed downstem. Others use a removable one.
The choice affects more than you’d think. Removable stems are easier to clean, easier to upgrade, and way more forgiving when something breaks.
If you crack a removable stem, you replace a $15 part instead of trashing a whole piece. That’s a no-brainer if you actually use your glass regularly and don’t treat it like a museum display.
They also let you experiment. Swap in a showerhead, try a multiplying rod, test different lengths or diffusion levels until you land on something that hits exactly how you want it to. And if you’re using accessories like ash catchers or reclaim adapters, a removable stem gives you more control over joint sizes and airflow.
Fixed downstems do have their place. They’re built-in, which means fewer parts to lose or damage. They tend to sit solid and won’t wiggle loose during use.
For travel bongs or small rigs where simplicity matters, they make sense. Just don’t expect to change how it hits or add new features later.
If you’re trying to build a setup that adapts with you over time, removable is the move. It’s functional, modular, and gives you more freedom without giving up performance. That’s what we focus on with every stem we make. It should work today and still work when you decide to change everything else.
Airflow, Diffusion & Drag: How to Balance the Hit
Airflow, diffusion, and drag are what decide whether your hit feels smooth, snappy, or like you're fighting a milkshake with your lungs. The terms get thrown around a lot, but here’s what they actually mean.
Chug is the resistance-heavy hit, deep, slow, and punchy.
Pull is your airflow. How easily can you clear the chamber?
Purr is that balanced, buttery draw where the stem hums as it diffuses smoke through water.
Different stems give you different mixes of those three. A stem with lots of tiny slits or arms might smooth out the hit, but it can also crank up the drag.
One person’s dream setup is another’s clogged mess. Some people go hard on multi-arm tree stems, then complain about “too much drag for not enough chug.” On the flip side, someone else rips a rocket stem with no percs and swears it’s the cleanest hit they’ve had.
The trick is to match airflow with your session style. If you want low-resistance, quick-clearing hits, TAG’s Super Slit Downstems and Showerhead models are dialed for that.
They’re engineered to spread smoke efficiently without blocking air. The result is diffusion that cools and softens the hit, but still gives you that “purr” instead of a wheeze.
A good downstem should make your bong feel alive. If your hit feels dead or overworked, the problem isn’t your lungs. It’s the path the smoke is taking to get there. Fix that, and everything else follows.
No Downtime with the Right Downstem
Most people overlook the downstem until they use one that actually works. That’s when it clicks. The airflow opens up, the hit cools down, and the whole session feels smoother.
Whether you’re after clean flavor, dense clouds, or a setup that just hits without fuss, the right downstem makes it happen. It’s a small upgrade with a big impact, and once you’ve dialed it in, there’s no going back to generic stock pieces.
If you’re ready to actually feel the difference, start with a stem that’s built right. TAG’s downstem collection is designed to give you options that are engineered for airflow, durability, and real-world function.
You don’t need to wonder what might work. You just need something that does.