Check the listing for details. PIEZO HEADPHONE FOR CRYSTAL AND REGEN RECEIVERS (HIGH IMPEDANCE). Condition: New. Listed at 15.98 USD. SO MAYBE YOU ARE LIKE ME AND SOMETIMES JUST NEED A SINGLE EARPIECE FOR LISTENING. I OFTEN NEED SOMETHING FOR TESTING OR A SHORT LISTENING SESSION AND WOULD RATHER NOT DEAL WITH A FULL BLOWN HEADSET. IN SUCH CASES THIS WORKS GREAT. I MAKE THESE FROM NEW PARTS, USING A FULL SIZE MALLORY PT-4175WQ PIEZO ELEMENT, LIKE THE ONE YOU SEE IN THE PHOTOS. I'VE SOLD TONS OF THESE OVER THE YEARS AND THUS FAR HAVE NEVER HAD A COMPLAINT. THIS MALLORY PIEZO ELEMENT IS QUITE SENSITIVE AND WILL WORK FOR BOTH CRYSTAL AND REGEN RADIOS. THEY ARE HIGH IMPEDANCE AND WILL SERVE AS A REPLACEMENT FOR THE OLD TRADITIONAL INDUCTIVE TYPE HEADPHONES IN THE 2 TO 4K OHM RANGE. I USE THEM FOR ALL THE REGEN RADIOS SOLD ON MY eBAY LISTINGS, WITH REALLY GOOD RESULTS. IN MY PERSONAL EXPERIENCE I HAVE FOUND THAT THE PIEZO ELEMENTS ARE OFTEN MORE SENSITIVE THAN THE OLD STYLE HIGH IMPEDANCE INDUCTIVE HEADSETS THAT HAVE BEEN USED SINCE THE EARLY 20TH CENTURY.