Character Co. Blog

How to Measure and Buy the Right Downstem

Know what to look for, and buy right


Downstems are an essential part of any bong or water pipe.  They function by transporting the smoke from the bowl or slide into the water chamber for a cooler and smoother hit.  Just like the bongs and water pipes they accompany, downstems come in a large variety of sizes, and styles.


Length: The lengths of downstems are measured from the top of the ground joint, all the way to the bottom. If the diffuser is a High Profile downstem, there will be an entire other section on top of the ground joint that doesn’t get included in the measurement. 

Ground joint: The ground joint is the sandblasted part of the glass attachment that fits snug with whatever piece it’s being connected to. Downstems have them. Bowls have them. Ash catchers will have them. Any glass on glass kind of piece will have a ground joint section that’s either male or female. See our post here.

Downstems Canada Character Co.

Diffuser:  A downstem on its own is already a diffuser by design. It’s literal existence is to carry the smoke into the water for filtration before being inhaled. However, it is almost industry standards these days to include some sort of extra filtration feature on a downstem, rather than simply keep the “straw” style that has only one hole at the bottom for the smoke to exit. As shown below, most downstems will have slits in the glass (the amount will vary) for extra diffusion.

Buying a new downstem

When buying a new downstem for your favourite piece, the most important thing to know is size, which can actually be pretty confusing if it is your first time buying a replacement.  When it comes to downstems, we can assume the ground joint is female, but there are 3 more measurements that you’ll need:

Length of the downstem

Size of the bongs ground joint

Bowl size  

Know Your Length

If you don’t have your current downstem available to measure the length, you can use a pencil or any long object that fits inside the bong/water pipe to measure the inner chamber of your bong. Remember not to go all the way to the bottom, there should always be at least a centimeter of space between the bottom of the downstem and the bottom of the bong.

Pencil Method

Insert the pencil into the inner chamber of the bong through the joint opening until the tip is roughly 2 cm or 0.5 inches from the glass on the other side.  Mark the pencil and then measure from the mark to the tip.  That will be your down-stem length.

Downstems Canada Character Co.

The Ground Joint

Measure the inside diameter of your bongs ground joint. It will be either 10mm, 14mm, or close to 19mm.  If you don’t have measuring tape nearby, you can use a dime.  If the dime fits through the hole, it is 19mm.  If it does not, it’s a 14mm or 10mm.  Chances are, it’ll be a 14mm as bongs with a 10mm ground joint are rare, and considered mini water-pipes.  

It is important to be sure of the correct size when ordering a new downstem:  wider joints obviously won’t fit, and narrower joints won’t create the air-tight seal you need for optimal performance.

Downstems Canada Character Co.

Bowl to Downstem Size

Downstems have one joint for the bowl and another to connect to the bong.  We already mentioned how to make sure the downstem will fit the bong, but how can you be sure the bowl will fit the downstem? This is the trickiest part, as the way of writing these measurements will vary from store to store.


Some of the more popular sizes are seen here:

14mm to 14mm (14/14) or (14>14)

18mm to 18mm (18/18) or (18>18)

14mm to 18mm (14/18) or (14>18)

18mm to 14mm (18/14) or (18>14)


The first number represents the size of the joint in your bong. The second number represents the size of the bowl. For example, if you see a description such as 14/18 or 14>18, this means your bong has a 14mm ground joint, and the downstem you’re looking at will hold an 18mm sized bowl.  Now you can fit a bigger bowl into that bong!

If the description was 18/14 or 18>14, your bong has a 18mm joint and the downstem will hold a 14mm bowl.

Two popular styles of downstems are the “Flush Mount” and “High Profile”.

Flush Mount Downstems

Have an opening that does not stick out much from the opening of the joint.  The length of Flush Mount Downstems are only a little longer than the length needed in the inner chamber of the bong.

High Profile Downstems

Stick out from the opening of the bong, and can sometimes add up to between 0.5 – 1.5″ inches to the length of the bong.


Now that you’re ready to purchase a replacement downstem diffuser for your bong. Check our accessories section in glassware for a downstem here

If there was anything we missed, please send us a note to, or find us on Facebook and shoot us a message. We would be more than happy to answer any questions.