audiophile vintage black plate soviet made 6as7g / 6h13c power tubes w/ coke bottle glass, old stock pairthe legendary thick dual-disc getters are the same found in holy grail reflektors, sony c800 mics + morethese highly durable long life tubes provide premium quality build and regarded sound output a natural sound stage w/ beautiful airy highs, excellent detail and clarity, and a rich warm tonality relaxed in vibe w/ spacious holographic sonics, accurate crisp imaging, and dense immediacysimilar to german variety w/ pin-point precision and no brittle harshness these russian made vintage tubes are a top choice and popular alternative to expensive european varietyalso popular in a variety of amps such as otl, bottlehead, woo audio, darkvoice, atma-sphere + more all tubes are twice tested, and undergo a complimentary refurbish and deoxit process ~ one of a kind quality control! full mutual gm conductance tested pair, several pairs in stock useful life test pass! (a key longetivity indicator) + leak / short / gas check give 100+ session hours w/ your specific amps voltage to fully settle-in / break-inships well packed worldwide w/ free economy postage! plain or branded boxes included ~ authentic vintage hifidelity audiophile / preamp / mic / power tube curation by caliacoustics~ see our website! new arrivals + limited special editions + rare true-nos sealed box + pinched waist rarities + high-resolution headphones