[miamicuse]

Garvin makes this 6" square junction box.

http://www.garvinindustries.com/Ele...-2-2-1-2-Deep-with-Conduit-Knockouts/6150-3-4

and you can get 6" mud rings like this:

http://www.garvinindustries.com/Ele...g-Device-Covers-Two-Gang-Device-Covers/61-1-2

But I couldn't find any 6" tall cover plates.

What am I missing?

 

[k_buz]

The picture shown isn't of a 6" mud ring, that looks to be a 4 11/16" mud ring. But that is of no matter. The device opening is standard no matter what size mud ring you install. A standard device and plate is all you need.

 

[NJMarine]

That is a 6x6 mud ring but as has stated a standard device and plate is all you need.
__________________

 

[Techy]

http://www.garvinindustries.com/Ele...Gang-Device-Covers-Two-Gang-Device-Covers/6BC

if you meant a blank cover...

 

[busman]

Kbuz is correct. That mud ring is for an 11B box.