How to Measure and Buy a Downstem: A Simple Sizing Guide

This is a simple guide to help you figure out what size downstem you need.

To measure a downstem correctly, you need two numbers: Joint Size and Length. Check the joint first. The standard size downstem for a bong is usually 14mm female joint, but it ranges from 10mm-18mm.

It can be very confusing on how to measure or figure out the size of your downstem, so this guide walks you through getting the perfect size for your bong.

What two measurements do you need?

To measure a downstem correctly, you need two numbers:

1. Joint size (diameter of opening)

- If you have ruler, measure across the top of the opening where the bowl and downstem connect

- If you don’t have a ruler, use the “dime test”

o 10mm – a dime won’t fit at all

o 14mm – a dime will fit about halfway into the opening

o 18mm – a dime will slide in comfortably and cover the opening

2. Length (distance from the bottom of the joint to the end)

- If you have a ruler and the original stem, start at the bottom of the joint (the joint is often frosted, though not always, and is the part your bowl slides into) and end at the diffuser tip

- If you don’t have the original stem, use the “pencil method”

o Insert a pencil into the open joint on your piece until it’s about half an inch

from the base (you don’t want it to quite touch)

o Use a sharpie to make a mark on your pencil where it exits the opening of

your piece

o Either bring the pencil in with ya or use it to measure from your mark to

the tip of the pencil

o Subtract 1 inch from that number to account for the joint length because

stems are measured from the joint down

Which is better: Diffused or Straight Downstem?

A diffused downstem gives smoother hits, while a straight downstem is easier to clean. Both work, so the choice comes down to your preference.

A straight downstem has one open end. The pull is a little bit harsher, the bubbles are a bit bigger, and the tube rinses clean in seconds.

A diffused downstem has slits or holes cut into the tip. The reason for the openings at the tip of the downstem is to create dozens of little bubbles, which creates a smoother, less harsh pull.

Where can you buy a Downstem?

The best option is to visit a local shop in-person, such as Up'n Smoke in Fort Collins, Colorado - which has staff that is very educated and well versed in this topic. Bringing your piece in to figure out the fit of downstem you need is a great option as well.