Installing Duct fro Bathroom

[niceg3s]

I need to run a 4" duct to the bathroom from the air handler. I have round registers in the house, but I've never installed one before. What parts will I need to do the work? I bought a 4" insulated flex duct so far.

I did fix the dust issue. One of the ducts had disconnected from the main trunk. I also caulked behind the register as there were gaps between the dry wall as some suggested.

[niceg3s]

If I look through the grill, it looks like it doesn't have a register box. Normally, I would just put in a box, but I want it to match the rest of the house.

[bentlimbs]

They make insulated cans that install from attic side of ceiling. You will need to know the size of your round register where it attaches to the box. Most likely you will have to go to a sheet metal shop and get this fabbed up. I haven't seen round registers in yrs.