So I already made the "Duct Flange 120mm & 3in" model to go on my exhaust fan for my hosing that leads to my window for my laser set up. I got a new enclosure [Comgrow] for my new setup, but not only is the exhaust tube much bigger than my hosing, but the mounting on the enclosure [for the fan] is smaller (100mm i think).

To avoid adding new holes in the enclosure for my fan (which would be the easiest route) I figured I would just remix the exhaust side duct to something for the induction side of the fan I could slide right over top of the exit tube that come with the enclosure. This would also make it easier for me to slide it off if I need to move the enclosure and not worry about unscrewing anything from the actual enclosure.

*THE WHITE PART IN THE PICTURES IS Comgrow_Adapter Model - PLATE 2 in Profile
The black adapter on the opposite side of the fan is this original 120mm fan vent and the other black part going in to this white adapter is the vent that comes with the Comgrow enclosure.

UPDATE - NEW DESIGN DIFFERENT APPROACH - PLATE 1 in Profile
I've attached a different model I was working [exhaust_fan_adapter] in order to make things a little easier for mounting, however it isn't exactly finished as I never put in the holes for the enclosure side (i drilled them by hand), but I figure i'd upload it anyway. It basically allows you to adapt the same fan to the inside and the original duct flange on the outside (again drilling your own holes for the enclosure mount spacing. Because of the weight of the fan (didn't want it pulling down on the enclosure fabric) it has a little extended piece on top so you can attach it to the enclosure frame using a small zip tie to help support the fan weight. At some point i'll add the holes for the enclosure side so you dont have to make them manually

See which one works for you application. I'd def be interested in feedback!