Handmade in Germany, ELROG vacuum tubes represent the pinnacle of performance for directly heated triodes and rectifiers.  The ER300B, ER274A/B and ER50 are unique in that hey are the only current production tubes of their type that utilise thoriated tungsten filaments.  The class leading performance of the ER211 and ER845 is taken further with the molybdenum metal plate versions, the ER242 and ER284.