This is the connector choice for SON dynamo.
This wiring harness is the heart of the kLite system, securely connecting your dynamo hub to the kLite lamp and USB charger, and including a toggle switch. No more fiddly DIY wiring solutions that break down during your first rainstorm / hailstorm / snowfield / bannock road mud situation / river crossing / etc. The kLite harness is ruggedized and designed for just these type of conditions.
The wiring harness is configured to keep the USB unit "always on" regardless of the position of the switch; the switch simply toggles the light on and off. This allows you to keep power to key devices like your trail GPS during night riding sessions and during the day, channel 100% of your dynamo power to charging devices through the USB charger.