This is a new Ericsson BSL-10 Slim Battery, which is compatible with Ericsson BSL-10, BSL-11, BUS-10 and BUS-11 type batteries and fits Ericsson T28, T29, T39, R320, R520, T28s, T29s, T39m, T28z, T28 World, T28sc, T29sc, R520M models.