This accessory is designed for exhausting 3D printer fumes to an 125mm air duct, but still being able to use the 125mm air duct for other purposes (like cooking).
One side is (1/3rd diameter) 123mm, so it fits in an 125mm air duct.
The other side is 100mm, so a standard 102mm air hose fits over it.
Supports required.
The author marked this model as their own original creation.