3849b6c8__and_Decker_Drill____GICL_Wiki__Reason_for_Material_Selection
[Part Name] Brushes [Quantity] 2 [Description] It is black, rectangular in shape with grooves. [Function] Helps complete motor's circuit [Material] Carbon [Reason for Appearance] Efficient wear design [Manufacturing Process] Extrusion [Reason for Material Selection] 
It is soft material to reduce damage, also conducts electricity.
Difference between revisions of "Group 12 - Black and Decker Drill" - GICL Wiki