1/4" flathead driver bit for use with O'Connor 3/8" camera tie-down screws
. Also known to work with other large slot head screws like on Arri bridgeplates, etc.
Printed tip dimensions come out to be 12.9mm x 2.1mm and are easily sanded if too thick.
Great camera assistants tool!
Check out the more universally compatible Camera Tie-Down Screw Driver Bit
and gimmicky Camera Screwdriver / Belt Buckle
in my shop.