These adapters fit over the top of the bottle stopper project mandrel threaded stud. They do not interfere with the threads as you can see in the picture. The #165 is 15/16″ diameter and fits the SS-620 whiskey stopper and other turning projects. The #164 is 1″ diameter can be used for the SS-630 top shelf Bourbon stopper and the Niles Bottle Cap Opener.
You can use the same washers you get with the mandrel for either of these because the washers are merely “spacers”, meaning they take up a bit of space so the wood doesn’t get a death grip on the mandrel.
These are made in my machine shop in MO so they are Precision made in the USA.