This is Sennheiser IE800 Ceramic In-Ear Earphone Shell for 6.5mm driver unit
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What are the Sennheiser IE 800?
The Sennheiser IE 800 are some of the most expensive universal earphones you can get. They cost £600, making them terrifyingly pricey for most people.
They don’t have the usual sound we expect from a really high-end earphones, though. With some of the deepest bass we’ve heard in IEMs they’re surprise party monsters.