Standard insulated, two conductor green cord with a rib on one conductor for polarity indication. 18 AWG SPT-1: 500 foot Spool, 18 gauge copper. Stranding: 41 strands/ 34 gauge. Insulation Thickness: 0.030?. Insulation Material: PVC. Working Voltage: 300V AC. Temperature Range: 105 degrees C. Size: Nominal O.D.: 0.104? x 0.210? UL Listed and CSA Approved. Wire only. Plugs and sockets sold separately.