A wire is composed of one or several flexible wires, wrapped with a light and soft protective layer; A cable is composed of one or several insulated wires, with a tough outer layer made of metal or rubber. Good quality wires are generally within the specified weight range. The commonly used plastic insulated single stranded copper core wire with a cross-sectional area of 1.5 has a weight of 1.8-1.9kg per 100m; 2.5 plastic insulated single stranded copper core wire, weighing 2.8-3.0kg per 100m; 4.0 plastic insulated single stranded copper core wire, with a weight of 4.1-4.2kg per 100m, etc. Poor quality wires have insufficient weight, either insufficient length, or excessive impurities in the copper core of the wires.