14.5 Ehle Diffuser Adapter for 1000 ml Bongs

Adapters by Ehle convince with their craftmanship and exact fitting. This adapter fits exactly onto the 1.000 ml bongs with 14.5mm ground joint.
Since all Ehle parts are handmade, the length of the stem may vary. Certainly we take care with new orders that the individual parts fit. In case you do have already an Ehle bong please tell us the length you need (length of stem without bowl). Thank you.
How can I measure the right length of the downpipe?