I'm on McMaster wanting to order some bx, figuring it would save me a trip to a store one evening this week, and they list two types of specifications:

AC/THHN and MC/THHN

I realize what the THHN means (the shielding around the conductors), but does anyone know what the AC or MC part or the specification means. I searched here and around the web.

I think it means that AC has the bonding wire integral with the metal shielding, but the MC does not and instead (if is is a 2 conductor cable) has a third unshielded copper conductor instead.

Just curious,

Thanks.