Second we must try first hand the desirability of a wire bent repeatedly any soft anti-fatigue and plastic or rubber flexible handle and wire insulation is no cracks in high-class product.

• 二要试，可取一根电线头用手反复弯曲，凡是手感柔软、抗疲劳强度好、塑料或橡胶手感弹性大且电线绝缘体上无裂痕的就是优等品。