Can this be inserted in a 2x4 wall without cutting a larger hole?

The Electrical box is 4” across, so you need a 4” hole & it will be ready to have fixtures attached to it. Technically, you could install it from the attic and make the hole smaller, but it’s a 4” electrical box, so you wouldn’t want a smaller hole.

This brace and box is compatible with old work applications (existing walls) and only a round 1-1/4 in. diameter hole is required for installation. Please view our product installation video for more details: https://www.hubbell.com/raco/en/Videos/RETRO-BRACE_Old-Work_Ceiling_Fan_Support.