The Bern Gallery

How to Figure Out the Size of Your Downstem

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Downstems are a vital part of your water pipe, and a great opportunity to do a little customization through perc choice or length options. However, a lot of people don’t think about this part until they need a replacement. Getting the right size ensures that the downstem fits in the bong properly, ensuring a good seal and proper percolation.

What Size Downstem Do I Need?

Downstem sizes are dependent on the dimensions of your bong or water pipe. Taking a few measurements and thinking about your preferences can help you choose the size you need.

There are also some pieces that have fixed downstems. Also referred to as “stemless” tubes, these ones do not have a removable downstem at all. Most downstems, the 10mm, 14mm and 18mm varieties, are ground glass or glass on glass joints, sometimes called GoG or scientific joints. 9.5mm downstems are for tubing/grommy style bongs and are more commonly found on cheaper pieces or on vintage pieces made before GoG style became common.

Downstem and Bowl Sizes

Downstems come in different diameters to ensure a secure fit. The most common diameters are:

  • 9.5mm, rubber grommet instead of ground glass, found on smaller and older tubes.
  • 10mm, a primarily oil related size less common for flower bowls.
  • 14mm, the most common size for downstem tubes.
  • 18mm, sometimes also called 19mm, more commonly found on stemless tubes.

Fixed-length downstems vary between 2.5 and 6.5 inches long when measured from the bottom of the frosted joint to the tip of the stem. However, we also offer the TitanStem, which is a precision-machined aluminum downstem with lengths that adjust from 2.5″ to 8.5″.

The length you need will likely be determined by the bong you have. Shorter bongs and bongs with smaller bases like straight tubes will use smaller downstems. Beakers and tall tubes generally use longer stems. Vertical bubblers with removable stems use the longest ones, some of them up to ten inches long.

Male vs Female Bowl Piece

The other thing to ensure is that you are getting the right bowls for your water pipe. Most downstems made today will be compatible with standard 14 or 18mm male jointed bowls and slides. You can occasionally find downstems with male joints on them intended to match with old school domes or with female flower bowls, but these are increasingly rare. Almost every modern piece is manufactured with a female joint on it, stemless or dowstem. 

How to Measure Downstem Size

Your downstem should fit in your pipe so that it enters the water in the chamber without hitting the bottom. The length of your downstem should be measured from the tip of the downstem to the end of the ground joint.

To measure your pipe, we recommend inserting a pencil into the joint. Push it as far down as you would like your downstem to fit. Then, hold your pencil against the place where the joint meets the inside of your water pipe. Mark and measure the length on your pencil, and you have your ideal length.

When it comes to diameter. One about the same diameter of your pinky finger should be 14mm; an 18mm downstem will be about the size of your thumb. 10mm joints are very small, and are usually very apparent to anyone familiar with the other two joint sizes.

If you want to get really precise, you have to do the math. Measure the circumference of your downstem, then divide by 3.14 (that’s pi to two places). The resulting number is your diameter.

Choosing the Right Downstem for Your Bowl

Once you know the diameter and length you want, all that’s left is picking out colors and features. At Bern Galleries, we offer attractive and high-quality downstems to complement your favorite glass. And, yes, we do custom orders. Take a look at our selection today.


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