I'd bend them to conform to the walls of the existing JB.

Agreed, note that these things aren't UL listed, so installation is at the discretion of your AHJ.

Thank you, gentlemen.

I know they are not UL listed, but our community's home inspector has directed us to use them in the past.

It turns out that I do have access to the rear of this (it is in a partial stud wall open to an unfinished closet), so I may try to rework or replace the box to be flush with the outer wall. My biggest problem is that the wall is about 1" thick with some fuzzy, fiberboard kind of wall covering that I have never seen before! I think I will need some extra-deep switch boxes to do that, however, because the boxes are connected to conduit, rather than AC or NM. (Hope I am making sense!)

Thanks again. Angie.

Is this a plastic box? There are other box extenders available in 2-gang, but most I've seen are plastic.

No, it is metal. Once I found out that I had access to the rear, I actually redid it properly. I pulled out the old switchboxes and put in deeper ones. Worked like a charm. Thanks so much for your help, Ron and Randy!