Is this for an E-body

[Katfish]

Defrost duct for rear package tray

[anlauto]

YES it is, both Cuda and Challenger 1970-74

[cuda hunter]

https://forum.e-bodies.org/cuda-and-challenger-general-discussion-roseville-moparts/2/need-picture-rear-window-defroster/6431/msg90325#msg90325

[Brads70]

Back in the day when my first Challenger was my daily driver, winter too. I remember the rear defroster being pretty much useless. After a couple of hours driving it cleared maybe a 6" area to see out of.  The big lug snow tires worked great though!