The Sylvania 6BK4C vacuum tube is a vintage electronic component manufactured in the United States by SYLVANIA. This unit is a single vacuum tube designed for use in vintage audio and video equipment. The model Sylvania 6BK4C is a sought-after piece for collectors and enthusiasts of vintage electronics, offering a piece of history from a well-known brand like SYLVANIA. APPEARS USED. BEING SOLD AS IS UNTEESTED.