Hi de dee. That is just a manual throttle lock. The clamp ring came from an old 10 speed bicycle seat height adjuster It fits loosely around the rubber grip, so that it can return to idle and when you move the clamp handle over with your thumb it locks down on the grip. The bottom of the clamp is anchored
between the two throttle cable housings. Quick and easy to put on and it works great. I love taking old junk and making something useful out of it.
Mac, aka "ole two wheels"