Schmidt Male 4.8mm connector

Basically this connector has one use.  You cut your headlight wire too short, and you need to extend it.  Get a pair of these connector by themselves if you already have two 4.8mm female connectors, or get them with the 4.8mm female connectors to extend your wire.  

Works basically like this: 

• If your headlight wire is too short, and already has Schmidt 4.8 mm female connectors, buy two male connectors and two female connectors.  Put the Male connectors on new piece of headlight wire, long enough to bridge the gap from your too short wire.  Install head shrink over the connectors, then plug them in to the female connectors coming out of the hub.  If you want to be extra safe, then install larger heat shrink over both of the connectors so it's all sealed up.  Then install the two new female connectors on the raw wire leads going to the hub, heat shrink those individually, plug it in!  
• If your wire is too short and you don't have female connectors on the light wire already, get 2 male connectors and 4 female connectors.  

First pic shows the male connectors by themselves.  They're sold individually, so if you are doing a light, you need two.  Second pic shows a female and male connector stuck together.  

The male connectors are kinda pricey, as it's a custom item hand soldered in Germany by tiny forest elves.