Tested status unknown. Estate find from a ham radio enthusiast. General Electric 5U4GB / 5AS4A rectifier vacuum tube with black base. Sold as-is, untested. No cracks in glass. Some visible wear from age. Ideal for audio restoration, hi-fi amps, or collectors. Thanks so much for visiting my store! I happily accept offers on most items?just click ?Make Offer!? Please note: I do not ship on weekends or holidays. Have any questions? I?m happy to help! Be sure to check out my other listings for more unique finds!