This is the adapter for the 10T cog.
Thread specifications:
Lower section: M30.5 x P1.0 (common cassette lock ring thread)
Upper section: M22 x P1.0
There are two versions, each is designed to fit the specific free hub.
Two versions:
For
Brompton 3 speed free hub (black color only)
For
Hubsmith 3 speed free hub (black color only)