16 guage steel With knockouts Mounting holes on back Two grounding emboss on sizes up to and including 24''x24''x6''; pre-punched grounding holes on larger sizes Grounding screw provided with each model Specify ''F'' for Flush mounting (example: DFUKO663) Knockouts (Conduit size): a=1/2''-3/4'' * b=3/4''-1'' ANSI/ASA61 grey polyester textured powder coating inside out