Audiophile pentode 4P1L (4П1Л) with direct heating is equivalent of tubes 4L1S / 4LS1 and a copy of the Wehrmacht tubes RL2 / 4P6. It is also direct replacement for the chinese 4P1S tubes. All available tubes were made in Svetlana factory. These tubes were used in many radio stations like R105, R109 etc., today they are mostly searched by audiophiles and used in different AMP projects. New in box. Years of production: 1960-1961.