This base is designed to hold 2 of the Bench Mountable 4-Jaw / 3-Jaw / 2-Jaw Vise with Swappable Jaws vises.
It is designed for vises printed at 75% scale.
You can see it in action here: https://www.youtube.com/shorts/Hw35rLNsROg
It is designed to be a direct fit on the 80mm chuck rotary jigs designed and sold at https://lightsource.pro/product-category/laser-accessories/
The author remixed this model.