Trip Spring or Return Spring.

Boss Part # MSC01509 Trip Wing Return Spring is used on Boss v-plows and straight blade RT3 plows. One end of your trip spring is attached to your push frame assembly on the plow, while the other end is attached to your trip return spring yoke assembly. Check your plow manual to ensure this is the trip spring you need for your plow. Boss makes multiple different trip springs for their many plows and they are not interchangeable.