11, 12, 21, and 23 single phase plugs, the Europlug, and types 15 and 25 three phase plugs. Former Yugoslavia This type of three phase plug and sockets are mainly used in households in former Yugoslavian countries, they are 5-pin 3-phase connectors, rated at 16 A, 380 V. Industrial 3-phase connectors are same as European IEC 60309. North America Pin and sleeve In North America, there are two types of pin and sleeve products that are used: NEMA The American pin and sleeve circular connectors are not compatible with the newer IEC 60309 type. Current ratings are 30, 60, 100, 200, and 400 A. All are rated for voltages up to 250 V DC or 600 V AC. Contact arrangements are from 2 to 4 pins. There are two styles depending on the treatment of the ground. Style 1 grounds only on the shell. Style 2 uses one of the contacts as well as the shell, internally connected together. They are not strongly typed for specific circuits and voltages as the IEC 309 are. One insert rotation option is available to prevent mating of similar connectors with different voltages. The contacts in the plug are simple cylinders (sleeves), while the pin contacts in the receptacle have the spring arrangement to hold contact pressure, the reverse of the IEC 60309 type connectors. All contacts are the same diameter. Originally metal construction was used, but now they are also made with plastic shells. Since only keying in the connector shell is used, and since the keys can be damaged in industrial use, it is possible to mis-match worn connectors. IEC IEC 60309 Series II (North American) pin and sleeve connectors have gained significant traction in North America over the course of the last 30 years . Series II current ratings are 20, 30, 60, 100, 200, 300, 350, 500 and 600 amps. The voltage ratings go up to 1000 V AC. These have been replacing the American-style for some time and are much more likely to be found in food processing, data centers, healthcare, entertainment, and other industries. NEMA connectors NEMA devices are not exclusively industrial devices, and some types are found in nearly all buildings in the United States. "Industrial-grade" connectors are constructed to meet or exceed the requirements of more stringent industry testing standards, and are more heavily built to withstand damage than residential and light commercial connectors of the