Clamp Back 1-1/4”, Malleable Iron
https://dev.nsiindustries.com/product/clamp-back-1-1-4-malleable-iron/
Bridgeport Clamp Backs are used to provide space between mounted conduit and mounting surface. Designed to be used with malleable or aluminum straps. Malleable iron construction offers the heaviest-duty solution with excellent impact resistance.