These units, introduced in the FT-9000 series, provide ultra-tight RF preselection thanks to the high Q (300 or more) afforded by the large 1.1 inch (28 mm) diameter coils used in filter construction. As the ferrite tuning slug is passed through the coil structure, the center frequency is adjusted, and the 3 dB bandwidth is approximately ± 12 kHz on 1.8 MHz.

They may used in a single or multiply connection