This is a genuine OEM supplied replacement part designed for use with drills/drivers. This screw helps to secure the chuck to the unit. This is a reverse thread, oval-head Torx screw, made out of metal and it is sold individually. Requires a Torx screwdriver to install or remove this screw.

Genuine Dewalt replacement part, this item is sold individually.
This screw is used in various places in all of the tools listed below
The most common use for this screw is to secure plastic housings together.
It has a Torx T-20 head.