Hose Fitting
To connect your ducting parts you can use either ducting clamps or just duct tape. Yet you need to be careful that they don't get disconnected in case of vibrations. So the heavy parts (the fan itself) really needs to be secured tightly, especially when they are mounted on the ceiling. If you have a high-capacity fan you may want to use insulated ducting to reduce the noise. If that does not suffice, add a silencer as well.
