14mm vs 19mm Bong Joints: Complete Size Guide

A bong joint is the ground-glass connection where two pieces of glass fit together. Instead of relying on rubber seals, many modern glass bongs use precisely shaped tapered glass joints.

You will commonly see joints used to connect:

• Downstems
• Cone pieces
• Ash catchers
• Bangers
• Glass adapters
• Other removable glass accessories

The important part is that the two connecting pieces need to be the correct matching size. A 14mm accessory is designed to fit a 14mm connection. A 19mm accessory requires the larger 19mm fitting.

A 14mm bong joint is the smaller of the two common fitting sizes. You may occasionally see it described elsewhere as 14.5mm, because ground-glass joints are manufactured to standardized dimensions. For everyday product descriptions, however, it is commonly shortened to 14mm.

At Billy Mate, we use 14mm because it is easier for customers to recognise and understand.

A 14mm fitting is commonly used for:

• Glass cone pieces
• Smaller bong joints
• Ash catchers
• Quartz bangers
• Adapters
• Smaller downstem connections

If the opening on your bong is relatively narrow, there is a good chance you are looking at a 14mm fitting.

A 19mm bong joint is the larger common fitting. It may also be described by some manufacturers as 18.8mm, but it is commonly rounded and sold as a 19mm joint. That is the terminology we use at Billy Mate.

The wider joint is often found where the bong itself connects to a removable downstem. This is where the term 19/14mm downstem becomes important.

This is probably the bong measurement that causes the most confusion. A 19/14mm downstem has two different-sized connections.

The 19mm end fits into the bong. The 14mm opening at the top accepts the cone piece.

So when you see 19/14mm, think: 19mm bong connection plus 14mm cone piece connection.

That makes it possible for a bong to use a relatively large downstem joint while still accepting the very common 14mm glass cone piece.

The exact configuration depends on the bong, so you should always check the product specifications rather than relying on appearance alone.

Joint size is only half of the equation. You also need to know whether the fitting is male or female.

Male Joint

A male glass joint is the tapered section that inserts into another fitting.

Female Joint

A female joint is the opening that receives the male fitting.

For example, a bong may have a female joint, while the downstem has the corresponding male ground-glass section. The size and connection type both need to match. A 14mm male fitting will not correctly replace a 19mm male fitting simply because both are made from glass.

The easiest option is to check the original bong specifications. Billy Mate product listings include joint sizes wherever possible so replacement accessories are easier to identify.

If you do not have the original specifications, you can measure the joint. Measure the diameter of the ground-glass connection, not the overall width of the surrounding glass.

Because glass joints are tapered, measurements can vary slightly depending on exactly where you measure. That is why you should think of the common standards as approximately:

• 14mm class: around 14 to 14.5mm
• 19mm class: around 18 to 19mm

A difference of several millimetres between these two fittings is quite noticeable once you know what you are looking for.

This is one of the most common mistakes. A 14mm and 19mm glass joint can look surprisingly similar in a photograph. Product photography also makes judging size difficult because there may be nothing beside the fitting to provide scale.

If you are ordering a replacement, check the specifications or measure the joint first. Trying to force an incorrectly sized glass fitting can damage either the accessory or the bong.

Another common source of confusion is mixing up joint size and stem length. They describe completely different things.

For example, a downstem might be listed as Billy Mate 19/14mm Diffused Glass Stem, 12cm. The 19/14mm measurement tells you about the glass connections. The 12cm measurement tells you the overall length of the stem.

Even if two downstems are both 19/14mm, they may not be interchangeable if one is significantly longer than the other. The correct replacement needs both the appropriate joint size and stem length.

Our next guide will explain exactly how to measure a bong downstem correctly.

This one is easy once you understand the notation. A 19/14mm downstem normally accepts a 14mm cone piece. The 19mm section goes into the bong. The 14mm section receives the cone piece.

So if you already know your Billy Mate bong uses a 19/14mm downstem and you are replacing only the cone piece, you will generally be looking for a 14mm glass cone piece.

Always check the product specification before ordering, particularly with third-party accessories.

An ash catcher also needs to match the bong's joint. You need to consider joint size, male or female connection and joint angle.

The angle is particularly important because ash catchers may be designed around fittings such as 45 degree or 90 degree joints. That means two ash catchers can both be 14mm but still be intended for very different bong designs.

We will cover this separately in our Ash Catcher Size and Angle Guide.

Yes. Glass adapters are available that allow certain 14mm and 19mm fittings to work together. However, using the correct fitting directly is usually simpler and creates a cleaner setup.

Adapters are most useful when you already own an accessory that does not match the joint on a different bong. Whenever an adapter is added, also consider the extra height and leverage it places on the glass joint.

You may notice some websites describe approximately the same fitting as 18mm, 18.8mm or 19mm. Billy Mate uses 19mm in product descriptions. It keeps the sizing system simple: 14mm and 19mm.

Where a downstem combines both sizes, we describe it as 19/14mm. This makes it easier to understand which side fits into the bong and which side accepts the cone piece.

If bong joint sizes are doing your head in, remember this:

• 14mm is the smaller fitting
• 19mm is the larger fitting
• A 19/14mm downstem is 19mm into the bong and 14mm for the cone piece

Then check the stem length separately. Once you understand those three things, choosing replacement bong parts becomes much easier.

When buying a replacement downstem, cone piece or accessory, check the full product specifications rather than selecting something purely because it looks similar. Pay particular attention to joint size, stem length, connection type and accessory angle.

Billy Mate offers a range of 14mm glass cone pieces, replacement glass downstems and bong ash catchers, with measurements included so you can match the joint size, connection type and length. If you are still choosing the bong itself, browse the full range of Billy Mate glass bongs, or read our companion guide Bong Sizes Explained: 20cm vs 25cm vs 30cm vs 35cm for help with height, stability and everyday use.

Billy's Tip: Before throwing away a broken stem, measure the old one first. Knowing both its joint size and length can save a lot of guessing when buying a replacement.