The 6B27 (often designated under the European system as EF83 or similar variations depending on manufacturer coding) is a 9-pin miniature sharp-cutoff pentode designed primarily for low-noise voltage amplification, wideband video stages, and specialty RF/IF applications in mid-century electronic equipment. Built on the noval miniature format, it provides high transconductance and low internal noise in small-signal amplification circuits. Operates on a 6.3V heater and fits standard 9-pin noval sockets. Available NOS and tested used.