These are genuine 2SK209-GR parts from Toshiba that have been pre-soldered onto an adapter so they can be used in through-hole layouts. They test within the same ranges as the obsolete 2SK117 and 2SK184 and will perform identically. They also have a blank white screenprint on the reverse side so that you can write in the Vgs(off) value, for example if you need to match them for a specific application.
You’ll have to solder in the legs yourself (clipped leads from resistors or diodes work great)—but this will get you most of the way there.
They are available in sets of 4 and 8. The sets are panelized, so they will need to be manually broken apart and tabs removed before use.
2SK117-GR and 1SK184-GR replacement
The Toshiba 2SK117 and 2SK184 JFETs were used in many Japanese effect pedal circuits in the 1970s and 1980s. These two JFETs have identical specifications, but different case styles. They were sub-classified based on their Idss specification, with yellow (Y) and green (GR) being the most common.
Most notably, the 2SK117-GR was used in the BOSS® OD-2 Overdrive, and the 2SK184-GR was used in the BD-2 Blues Driver and OD-3 Overdrive. Toshiba no longer manufactures through-hole JFETs, and the 2SK117 and 2SK184 have been out of production for many years.
However, there’s a catch: while most USA manufacturers will only change the prefix to distinguish through-hole from surface-mount parts, e.g. 2N5457 and MMBF5457, Toshiba’s practice is to change the whole part number. And if you compare the datasheets, the 2SK209A shares the exact same specifications and sub-classifications as the 2SK117 and 2SK184. They also measure in the exact same ranges as the parts used in vintage units.
So in other words: the 2SK209-GR is not just a substitute for the 2SK117 and 2SK184. It’s the same part manufactured with the same process, just in a different package.