Common on European utility bikes, a front wheel stabiliser makes loading front racks simpler.
It is a spring connecting the fork to the down tube. It adds a subtle self centering action to the front wheel, making loading and unloading of a bike with a basket, or say....our Porteur rack....much easier. You don't fight the bike while putting stuff in it. The front of the bike stays put. The spring offers some resistance to steering, so it counteracts deflections from hitting potholes and road debris, too.
It's pretty universal - any bike with a down tube of 1-1/4" (31.8mm) or smaller be fitted. It connects to the fork via the brake pivot hole. The hole diameter is made for nutted calipers or a M6 bolt. For recessed mount calipers, minor modification with a drill or a file is necessary.
The wheel stabilizer is rust resistant, includes all the required brackets and hardware, and has a pinch guard to cover the torsion spring. The little knob adjusts the spring tension.