This quality bass soundpost for ¾ size upright bass is made of quality, properly dried spruce (no "green" wood here!)
We now have two diameters; the more commonly used one is approximately 3/4 inch or 19mm. We also have a slightly smaller model, which is 16mm - you might find this better for a smaller-bodied instrument, or to alter the timbre of the instrument with a smaller footprint.
They are around 14" long, you shorten it to fit your instrument. A great replacement for your broken or lost soundpost. We can get cheaper sound posts, but it seems silly to me to spend the time fitting a cheap woodpost-old spruce is best! We have the traditional bass soundpost setter available as well.
We also have a few left that we acquired from Engelhardt before they closed up shop. They are shorter, but still good wood - they can be added to the cart if they are still available, and are discounted. They are 19mm by a touch over 9.75" long.