SLB101 Switch Box, 1-Gang, SliderBar Type, 3.715 x 3 x 2.225", Non-Metallic

Switch Box, 1-Gang, Slider Bar Type, 3.715 x 3 x 2.22 Inch, Non-Metallic, For Use With Arlington SliderBar Adjustable Bar Hangers

Here's the easy, NEAT way to mount a single or two-gang box between wood or metal studs with non-standard spacing. It's adjustable to fit between studs spaced 12 to 24 inches apart, depending on SliderBar used, and allows you to position one or multiple boxes where you need them in the stud cavity.