These 6AM6S tubes are compatible with Little Dot headphone amps and tube buffers using the EF91 / 6AM6 / M8083 tube. These French made 6AM6S have an incredible very detailed low noise floor and are probably the best sounding 6AM6S PM07 EF91. Special quality French made early 1960's. We have several hundred pcs in stock so as always extremely tight matching available. All tested on Amplitrex AT-1000. Enter qty for matched pair. Just $23.99 each!