Behind Can Vent?

[FiretruckGMC]

So i had this problem today,im not sure what its called but its the black plastic vent on the back of the cab, well it fell off there was ice built up on it and i went to knock it off and it fell out. what is it called, where can i get a replacement or how do i put it back in....

[Silverado4x4]

That vent is for to keep pressure from building up in the cab with the Climate system running and its also for cab ventilation. Some are screwed in with little screws and some just snap back in. You might just put in back in and if it doesnt stay just get some Silicone adhesive and stick it back in.