1, look at the protective door, stabbed with a screwdriver or a small key two holes and three holes in the bottom side just a hole. With some effort, was stabbed into the protective door is unilateral, equal to none. This outlet was not enough security. 2. Second, look at copper materials. If you see a bright yellow by the jack, then give it directly. Brass easily rust, texture soft, over time contacting conductivity will decrease. If the copper color is purple is better, copper relatively tough, not easily rust. Direct look is not enough, the general also open look. Many outlets are jack used here copper, brass inside are equally susceptible to rust. Even copper are used, there are hierarchical. Most brands of copper pieces are a good few stitching, rivets interface so that the interface will be fever, affect the conductivity. Technical Compare now into the brand will be used to do the whole piece of copper inside the copper pieces, so a lot of the conductivity increase. 3. Third, look at the distance between two or three plug it. Some products are not considered so much, two holes and three holes from the more recent, plug the three holes, two holes becomes furnishings, because the plug is large, the local accounts. These issues must be considered when buying outlet clear.