Genuine Milwaukee replacement part, this item is sold individually.
This is part of the blade clamp assembly for the Milwaukee Sawzalls shown below.
It is used in combination with the part number 42-68-0677 Blade Clamp.
For extra convenience you can order the 3/16 Allen Wrench 49-96-0080 for the screw, and the 48-66-4080 Allen Wrench Holder.