Medium output rectifier tube originally used in early medium power Fender amps with tube rectifiers. This rugged tube is a favorite with high-end guitar amp repair experts and boutique amp gurus because it does not rattle in loud combo amps. Tube is imprinted exactly as depicted. Manufactured in Russia 2016. Operationally tested by Angela Instruments. We want the tube to work in your amp so we test 'em in ours. Not just once, not just twice but THREE TIMES. If the tube fails in normal service within 12 months send it back to us and we'll replace it once. Why so cheap? We bought a big bunch of these from Fender Groove Tubes 'bulk packed' in crates of 100 tubes. Each tube you purchase will be expertly boxed by us for safe shipment. Since 1977 Angela Instruments has shipped many thousands of rare and fragile items worldwide.