This unused, old stock 12AX7 was made by Shuguang in the now closed Beijing factory before they moved to Changsha. They are the highly sought after version that are no longer made and getting difficult to find. It is a high quality preamp tube and is regarded for its clarity and brightness. These tubes are OEM which means they were intended for installation in new production amplifiers and have no printing on the glass. They are stock tubes in many amps including Marshall and Mesa Boogie. Considered by many to be the best sounding preamp tube available.