A thing to mount a centrifugal fan with an outlet of 40x30mm (outer measurements) on a plate (or terrarium, box, ...) with 3mm wall-thickness. Includes a flap valve (requires vertical fan installation).Make sure that the flap valve rotates fully back without assistance. sanding paper and/or more infill could help if the problem persists.It's easy to modify the model. Therefore, if you need it with other dimensions (wall/outlet) - tell me which and I will upload it for you ;)