Medium output rectifier tube originally used in early medium power Fender amps with tube rectifiers. Manufactured in Russia. We bought a big bunch of these from Fender Groove Tubes 'bulk packed' in crates of 100 tubes. No Groove Tube logo. 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.