ASTM B-3 Soft or Annealed Copper Wire.  ASTM B-3 Specification details the requirements for solid wires and the individual wires in stranded conductors.

ASTM B-8 Concentric - Lay - Stranded Copper Conductors

Solid or stranded 100% conductivity copper conductors. 

Application

Used for bonding and grounding electrical circuits and systems.