Shimano hub dynamo connector
The Shimano hub dynamo connector looks like a very small Lego brick
It connects to the Shimano hub dynamo. Occasionally they have been known to work loose and fall off - which is why we offer this spare part!
Compatible with both SP and Brompton Shimano and Nexus Shimano hub dynamos
Section 3c of the download document shows how it works.
The below video shows how the Brompton Shimano hub dynamo connector works