[KiWinUS]

It has a 3/8 drive square as well as the 15/16 external hex. I wanted it to grip at the base of stud as close to the deck as possible so I bored the center out with an end mill ( it’s hard). Now it drops all way down on stud. As well as impact I used a 1 7/16!wrench briefly on outer housing. Probably not needed with impact as once it starts to grip it keeps tightening its grip. It never slipped.