Product Description This white 18 AWG (American Wire Gauge) 2 conductor Speaker cable is CMP rated for plenum spaces. This 1000 foot bulk cable comes on a spool and is ideal for wiring the speakers in your home theater, office or house to your receiver and/or other AV equipment. Each conductor (wire) is composed of 7 0.386 mm strands made from pure copper which provides the optimal conductivity/low resistance to drive high quality audio to your speakers. Cables that do not have a jacket rated for in wall or plenum use could actually cause the fire to become more intense. Plenum rated cables are jacketed with a fire-retardant plastic jacket of either a low-smoke polyvinyl chloride (PVC) or a fluorinated ethylene polymer (FEP) for less toxicity during a fire. If a fire gets into a plenum rated area that contains plenum rated cables and the fire spreads, the cables will not be to blame. Plenum rated cables can help prevent the spread of fires. Our speaker wire is made from pure copper. Some companies use the marketing term oxygen free copper which really means there is no iron oxide in the wire. When oxides of iron are in the copper, the conductivity of the wire reduces due to the higher resistance of the iron oxide. So it is in your best interest to install speaker wire made with pure copper like ours are. Another misnomer is that copper clad aluminum is the same quality as pure copper; this is false. The resistance (Ohms) between the two differ and as resistance in the cable increases the power delivered to the speaker is reduced. The sound will be lower and can lose some of its quality. If copper's conductivity, due to resistance, is rated at 100% then aluminum's conductivity would be rated at 61%. In order to deliver the same quality of sound with aluminum one would need a much larger gauge.