This isthe Tripler Base to take 3 stacks of Wemos D1 Mini compatible shield and modules. These Base is in technically terms a “back plane”, and it connects the pins with the same names and functions between the 3 stacks.
It also comes with a large prototyping area, using all the available space between the header rows.
The use of such a Base makes it much easier to build larger projects, than stacking everything piggyback on top of each other.
The Tripler Base comes with the necessary 6 connectors for D1 Mini compatible modules and shields.