The Groove Tubes Silver Series ST-12AX7-R Preamp Tube is intended as a replacement for tubes that will receive normal service. Country of origin: RussiaNEW SILVER SERIES TUBES Groove Tubes Silver Series are tested and warranted to meet or exceed factory specifications. Silver Series tubes are excellent for "normal" tube replacement applications and offer exceptional value. Not recommended for the critical high gain V1 stages of high gain guitar amps, but perfect for the other less critical stages such as V2-V6 stages. Country of origin: Russia