They are fairly new to the UK,but are becoming popular.
They have two hooks attached from the head end,and are balanced in the middle.When they are slow jigged they have a flutter down effect because of the way they are balanced.
The hooks have an inline eye instead of the conventional crossway eye.
That type of hook is ideal for stinger rigs that are attached by about 6" of line from the main(larger hook)
Small bait on the stinger hook and larger bait on the bigger hook.
I'll be giving them a try this year.