In Windy City Wire cables, the 2BC designation indicates a dual-braid shield, with both braids made from uninsulated (bare) copper. Dual braids increase overall coverage and lower transfer impedance compared to a single braid, which helps reduce noise pickup in demanding AV, security, and control environments.
Bare copper offers excellent conductivity and straightforward grounding. (Tinned copper is used primarily for corrosion resistance and solderability; 2BC refers specifically to bare copper.)