transitioning from 6" round to toe kick

Can anyone suggest the proper way to do this? Is there a standard fitting to accomplish this? The 6" round is stubbed off in a joist bay at present so all options are available.

Thank you,

Keith McKinley

Try this ductwork diagram.

Same diagram with interactive rollover for details.

Register boot detail.

6" round to a 3" x 12" will not cause excessive friction loss.

Thanks gentleman! In my mind I was making it a lot harder than it needed to be! I’ll use a 6" 90 to the 6" to 3x12 transition and just extend the box (if needed) to my toe kick. Perfect!

Appreciate your time!