1. Look at the protection door, with a screwdriver or a small key to poke two holes on one side and three holes in the bottom of a hole, with a point of strength, stabbed into the door is a unilateral protection, this socket is obviously not safe.
2. See copper pieces of materials, if through the hole to see is bright yellow, that directly give up, brass easily rusty, soft texture, time a long contact, conductive performance will decline, if the copper color is purple red is better, copper more toughness, not easily rusty.
3. Look at the distance between two or three plug, some products did not consider so much, the two-hole and three-hole distance is closer, inserted three holes, the two holes are changed, because the plug big, the place accounted for, these problems in the purchase of sockets must be considered clearly.