The connector of general electronic products and the pin of electrical products are called plugs. Household AC power plug and socket, with rod-shaped or copper plate-shaped protruding male connector, which is physically inserted into the female connector type power socket with slot or recess. Size is an important technical requirement related to whether the plug, socket and converter can be used safely and meet the general interchangeability requirements to avoid misinsertion. Unqualified size will affect the user’s use or produce hidden dangers such as poor contact and wrong insertion. At least, the equipment will be damaged, and at worst, fire and electric shock accidents will occur.