Product overview These are matched pairs of 6K4 vacuum tubes designed for reliable audio performance and easy replacement in compatible equipment. Each package contains two fully tested and matched tubes ready for installation. Key benefits Improved clarity and detail: Natural sound reproduction with a focus on midrange clarity for clearer vocals and instruments. Wider soundstage and stronger bass: Expanded imaging and a more pronounced low end make complex recordings sound more defined. Low noise and smooth end: fidelity, soft tonality with low background noise for less listener fatigue. Reliable and stable operation: Built for consistent performance across sessions. Compatibility Direct replacements for 7pin 5654, 6AK5, 6AK5W, 6Zh1P, 6J1, 6J1P. Can directly WE403A, WE403B, EF95, and ordinary 5654 tubes. Suitable as replacement tubes in equipment using 6J2, 6J3, 6J4, 6J5, or 6K5 designs. Construction and materials Constructed with a quality glass envelope and precision internal metal components for stable electrical characteristics and durability. Each tube is fully tested and matched in pairs to maintain balanced stereo performance. Typical applications Hifi tube amplifiers: Upgrade or restore preamplifier stages to improve clarity and soundstage. Vintage radio and receiver restoration: worn or failed 7pin tubes with a compatible 6K4 pair. Studio and signal processing equipment: Use in audio gear that requires these 7pin equivalents for consistent lownoise performance. What you get One pair of matched 6K4 vacuum tubes, tested for performance and matched for stereo balance. Notes Verify socket type and pinout compatibility before installation. These tubes are intended for audio and electronic equipment that specifies the listed compatible tube types.