Thomas & Betts 3060 3-1/2" Round Box With Nails Thomas & Betts 3060 3-1/2" Round Box With Nails Features: Round reinforced Phenolic outlet box Mounted by nails or screw mount 3-7/16" outside diameter 150º C heat rated material Classified for two-hour fire wall or fire ceiling No knockouts 3-1/2" diameter