This is meant to be a hose collar for 4.25inch flexible ducting. It is meant to hold a hose against a metal housing and there are channels for magnets or double sided tape to hold the collar against whatever outlet vent you have. The channels are a little over 10mm wide and 3.5mm deep.

The two halves are intended to be held together with glued in magnets. The indent for the magets are 22mm in diameter and a little over 5mm deep (5.3mm). If you are unsatisfied with this solution you could certainly drill a hole through each side and screw the two sides together, or modify the model in such a way as to provide this feature.

If you need a tighter seal, I would recommend adding a gasket between the collar and whatever surface you are mating it to. The original application for this is to vent the fumes from a peopoly phenom SLA 3d printer. If this is your application, as well, it should work quite well.