Defrost ducts

You can get the regular black ducting tube at any auto parts store as well. I believe the outlet from the heater box is bigger than the outlet from the defroster vent up on the dash. The tube will fit snugly inside of the heater box outlet and then snugly on the outside of the vent on the dash. Don't worry about it sitting inside of the heater box outlet, you'll never notice it restricting any of the air flow.

I believe it comes as one long piece and you cut it to whatever length you need.