Bong Downstem Sizes: How to Measure Your Pipe

Downstems are an essential part of any bong. They're the bit that reaches down into the belly of your pipe and gives you that all-important airflow to filter and cool your smoke. Unfortunately, downstems can also break. No need to fear! If you've got a new bong or a recently broken older one, here's our step-by-step guide for how to measure a downstem to get the perfect new bowl piece.

Step 1: Gather Your Supplies

This step is easy — you don't need many supplies. The most important piece to have is, obviously, your bong.

Next, grab a ruler or measuring tape. If you don't have either of those, get a pencil and a penny. (Try your couch cushions for these.) Bong downstem sizes are fairly straightforward: the most common are 10mm, 14mm, and 18mm. Your pencil and coin are a key part of how to measure a downstem.

Step 2: Check Your Joint

A penny is almost exactly 19mm in diameter. You're going to use your coin to figure out your joint size.

Start with the female ground joint of your bong. If you can barely get a side of the penny into the joint, it's 10mm (or if you can't slide a pencil into it). If the penny fits in about ¼ of the way, it's a 14mm joint. If it fits about halfway, it's an 18mm joint.

Need to measure bong downstem sizes for a male joint? Similar sizing applies. If your joint covers a small fraction of the penny, it's 10mm. If it covers about ¾ of the penny, it's 14mm. If it covers almost all of the penny, it's 18mm.

Step 3: Find the Length of Your Downstem

Learning how to measure a downstem includes the length. This is where your pencil comes in.

Insert the pencil into the female ground joint of your bong so the tip hovers about ½” above the bottom. Ideally, it would hit the water should the pipe be full. Make a mark on the side of the pencil where it exits the joint.

Now, to measure your bong downstem size, measure from the tip of the pencil to that mark. Keep in mind that downstem measurements typically don't include the length of the glass ground joint. These joints are usually one inch long, so you'll want to subtract that from the measurement you took from your pencil to get the perfect length.

Don't have a ruler? Remember that pennies are 19mm wide. Count how many pennies fit from the tip of the pencil to your mark and multiply by 19 to get an approximate measurement (remember to subtract 1 inch or 25 mm).

If you have a 10mm joint and can't fit a pencil inside, other options include the ink reservoir of a pen or you can maybe tape some toothpicks together in a pinch.

That's it, now you know how to measure a downstem!

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