There are 3 types:

• Single lead: designed to connect one device (either a USB charger or a front light) to the dynamo hub
• Switch/loom lights or USB: designed to connect both a front light and a USB charger to the dynamo hub. The switch will divert the power to either the front light or the USB charger - not both at the same time.
• Switch/loom USB always on: this will connect both a front light and USB charger to the dynamo hub, however the switch just turns the front light on and off - it will not affect the USB charger, which will deliver power whenever a device is plugged into it. If you are planning on running a Klite Qube safety light this is the version you need.

Each of these 3 types is available for Schmidt SON hubs (which have two prongs protruding from the hub) or SP/Shimano hubs (which use a little clip that goes over the terminals).