It's called the Glass Threaded Adapter.
Patent Pending and compatible with medium base bulbs.

Allied Maker's mission is to deliver artisan crafted, highly engineered, sophisticated, yet simple lighting design solutions. Over the past year, we have been elevating our entire collection to stand proud in the world of luxury decorative arts yet be user-friendly and priced right for the commercial and hospitality designer. Our most recent innovation advances the company's mission to the next level. It's called the Glass Threaded Adapter. It allows our artisan blown-glass to be easily threaded on and off. This results in less damage, less installation and maintenance costs, and ultimately a much more elevated lighting fixture which is holistically designed from creation to installation.