Miche's unique system allows for a fast change of sprocket ratios. 
The splined adaptor screws onto the hub just like a normal cog, then simply slide the sprocket onto the carrier. Then both carrier and sprocket are held in place with the lockring. To change the ratio, simply undo the lockring and remove the sprocket. Slide on a different tooth size and refit the lockring.
Because of the smaller diameter of a 13t sprocket, the actual sprocket is threaded and cannot be run with carrier.
Made from Opaque chrome-plated steel
Carrier is not supplied with MS16K, MS17K and MS18K
Lockring sold separately