For distribution arresters, which are mainly used with classes 5 kA and 10 kA, the nominal discharge current represents a real differentiating characteristic. When carrying out an operating duty test, the energy into a 5-kA-arrester is injected in the form of two high current impulses of 65 kA each, after it has previously been conditioned with 20 lightning current impulses of 5 kA (which is its nominal discharge current). With the 10-kA-arrester, on the other hand, the appropriate value of the high current impulses is 100 kA, and the value of the lightning current impulses is 10 kA. Since this means a considerable energetic stress for the small MO resistors (with diameters in the range of less than 30 mm to up to 45 mm), as are used for distribution arresters, a 10-kA-arrester must indeed be equipped with larger volume MO resistors than those needed for a 5 kA type, in order to pass this test. For central European distribution systems, 5-kA-arresters are completely adequate. Only in exceptional cases (e.g., because of an above average keraunic level) is the use of 10-kA-arresters recommended. In practice the 10-kA-arrester is becoming ever more common, as the price difference between the two types diminishes, while at the same time there are logistic advantages to using only one arrester type for the entire system.