This is a 12AX7-R vacuum tube from GROOVE TUBE, which was acquired by Fender. I purchased it about 10 years ago as a replacement for amplifiers and effectors that use vacuum tubes. I've used it a few times as a replacement, but I haven't used it permanently for years. After that, due to the rapid advancement of digital technology, I had no opportunity to use it and have been storing it. Here's a product introduction from the import agent CFE at the time: ////////////// This R tube is known for its outstanding stability and durability, and is standard equipment in Fender amps. This is the 12AX7 tube with high reliability. It will transform high-gain amps and bright-sounding amps into warm-sounding amps. Thick, full sound. If you're unsure which preamp tube to choose, this 12AX7-R tube is a safe bet! Made in Russia. Customer Reviews: "The sound is clear across the entire range, and the high frequencies are a bit prominent, but not piercing. It's a sparkly feeling, lol. The mid-range loses a bit of thickness and becomes flat. The low frequencies become thicker, going from 'doo, doo' to 'dong! dong!' and become powerful with good clarity. It's a vacuum tube that produces a clear and energetic sound with a decent amount of thickness."