How To Find The Correct Joint Size For Your Bong
4 min

How To Find The Correct Joint Size For Your Bong

4 min

Understanding joint size is key to understanding what pieces of equipment your bong needs. Regardless of the shape and configuration of your bong, knowing the joint size will enable you to buy the proper downstem and/or bowl for your device.

Whether through breakage, loss, or just a desire to update, you may well want to add a new downstem and/or bowl to your bong setup at some point. To do this, you have to understand what kind of joint your bong has, and what size it is, otherwise you might end up with the wrong bit of kit.

In this article, we explain how to do this.

Anatomy of a bong

Anatomy Of A Bong

If you need to replace parts of a bong, then you have to know a little about bong anatomy, and exactly what your bong requires. Bongs come in different sizes, and depending on what material they are made out of, the specifics of each part can vary. Below, we’ll go into detail about three (usually) separate and removable parts of bongs that you might need to replace or update at some point.



The downstem goes through the body of the bong into the water chamber. On top of it sits the bowl, where cannabis is burnt.

First off, in some bongs, the downstem is fixed to the body, so it can’t be replaced. This is most often the case with glass bongs. If you already have a bong, take a look at it to see if the downstem can be removed.

If you can replace the downstem, then there are some factors you need to consider.

First, you have to know the diameter of the hole that the downstem will go through. If you randomly choose one, then it may be either too wide or too narrow to fit your bong, and thus will be useless. In the Zamnesia store, all of this information will be contained in a datasheet on the product page. If you don’t know what your bong is called and don’t know its measurements, you should measure the diameter of the hole yourself to ensure you buy the right downstem.

Another factor to bear in mind is the size of your bowl. If you have an existing bowl that you’d like to reuse, you need to know how big it is and match it up with the joint of your new downstem. For glass downstems and bowls, this is called the “ground joint”. Some will have bowls attached, others will not.



If you’re looking for a replacement bowl, then the first step is to match up the materials. Glass downstems use glass bowls, and metal downstems use metal bowls. Then, you have to know the size of the joint. As mentioned, with glass bongs, this is called the “ground joint”. With metal ones it could have different names, but just make sure you know the diameter of both the bowl and stem.

Usually, in the case of metal ones, you would buy both together anyway. It can be hard to find metal downstems or metal bowls for sale without one another.

Beyond the size, you may want a bowl to come with some extras. For instance, you could buy a glass bowl with an ash catcher fitted inside, which will make the smoking experience smoother. If you’re buying metal equipment, you might want to buy a pack of gauzes to fulfil the same function.

Bong joints

Bong joints

A little more detail about bong joints. When using metal downstems, they typically go directly through the bong and are sealed by a rubber grommet. With glass bongs and downstems, it’s more likely that the downstem will attach and seal via a ground joint. These are tapered glass joints. The bong is usually female, and the downstem male, meaning the downstem will fit into the bong. If they are the same size, then they will seal properly. If not, then they won’t fit.

Note that the ground joint is often not the same diameter as the output of the downstem, and so you may need to look for the specific measurements.

Related article

What To Consider When Buying A (First) Bong

How to measure your bong bowl or joint size

So, if you have a bong but need to find out how big it is and whether it has a male or female configuration, here’s how to uncover what’s going on.

Male & female

Male & Female

First, find out if your joint is male or female.

A female joint will be ground (rough) on the inside, and will appear to open up. The point attached to the bong or top of the downstem (if you’re looking for a new bowl) will be the narrowest, opening to a wide top.

A male joint will be ground on the outside and will taper a narrower opening. This way, it can fit comfortably inside the female joint.

Measuring joint size

Measuring Joint Size

Joints come in three standard sizes: 10mm, 14mm, and 18mm.

The good news is that almost all bongs that fall within the “normal” size range use 14mm ground joints. So that’s probably what you need. Only the smallest bongs and dab rigs use 10mm joints, and only the largest use 18mm.

To measure joint size, you can just use a tape measure to measure, in millimetres, the distance between the inside edges of the joint. If you don’t have a tape measure, you can also use coins to gauge the distance.

If you’re in the EU, you can use a one cent coin. They measure around 16.5mm in diameter. Therefore, if they can drop inside your joint, then it’s an 18mm joint. If not, it’s either 14mm or 10mm. From this point, if you’re using a coin, you’ll just have to estimate which it is.

If you’re in the UK, then you use a five pence piece. Now, these measure 18mm, so they won’t drop inside a joint, but you should be able to fit them into the biggest up to their middle (widest point). If they block before the middle, then you have a 14 or 10mm joint. Again, you’ll need to estimate somewhat to figure out which it is, if you don’t have a measuring tape.

Related article

Why Bongs Have Different Shapes

Finding the right accessories and replacements for your bong

Finding The Right Accessories And Replacements For Your Bong

With this info, you should be able to choose the correct replacements to update your bong’s downstem and bowl. But why not branch out and get some more accessories? Perhaps try a downstem with an included diffuser to help cool your smoke even more.

Or, if not, just stick to the basics and make sure to keep them clean with pipe cleaners and bong cleaning solution, otherwise your smoke will soon begin to taste bad.

Knowing how big the joints on your bong are is really important when it comes to matching new downstems and bowls. Get it wrong, and you’ll find that your new equipment is useless to you!

Max Sargent
Max Sargent
Max has been writing for over a decade, and has come into cannabis and psychedelic journalism in the last few years. Writing for companies such as Zamnesia, Royal Queen Seeds, Cannaconnection, Gorilla Seeds, MushMagic and more, he has experience in a broad spectrum of the industry.
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