I don't know what they are, in all honesty. They came off of a friend's Steinberger Synapse, he said I could have them… but I don't have a headless bass.
They are flatwound, feel like medium gauge, have no fret indentations (it was a fretless).
The balls on both ends are both silver.
I'm sure that there are only a few companies that even make such a beast, so your guess is as good as mine… $12 OBO shipped anywhere in the US.
Will only work with headless systems. If you have a 4 string, just throw the 5 away or BEAD tune… that's up to you