Threadless headset system fork internal Starnut for pre-loading bearings.
Item features 2 layers of steel sprung tangs. 
Starnut knocked into place and the tangs bite into the fork to prevent extraction when a central headset adjusting bolt is tightened.
Fits regular steel or alloy 1 1/8" (28.6mm) external diameter fork steerer tubes.
Warning:
Do not use on Carbon steerer tube forks. The sharp spring metal tangs can damage the delicate Carbon structure.

Two types are available
Regular solid bolt option with M6 internal thread
Hollow freestyle M10 threaded bolt for passing front cable through the headset.

(Bulk workshop packing)