Crystal Earphones are extremely sensitive and require so little power to operate that you can hear a small 'click' just by touching the two bare leads together. Crystal radios will not work with modern earphones or 'earbuds' as they are designed to operate with high power circuitry found in today's electronic devices. Like many crystal radio parts, Crystal Earphones are not all that easy to keep in stock and finding decent ones is not that easy. Our Crystal Earphones will work great with any crystal radio. We test each one in a crystal radio circuit to verify it works and meets our specifications. Limited quantities available.