This specification covers the performance requirements for NPN, silicon, low-power transistors. Four levels of product assurance are provided for each device type as specified in MIL-PRF-19500. Two levels of product assurance are provided for die. RHA level designators “E”, “K”, “U”, \"M\", \"D\", \"P\", \"L\", \"R\", \"F\", \"G\" and \"H\" are appended to the device prefix to identify devices, which have passed RHA requirements.