This spinner fits the 45" radio controlled Miles M.20 model of my design. This model was released as a free digital plan in the July 2015 issue of Model Aviation magazine. This is a 2-piece assembly. The nose cone snaps into the backing plate. The cone's OD is 82mm. The length is 64mm. This spinner works well with an eFlite 4mm prop adapter. NOTE: the spinner plate has been improved by adding two thin cylinders to the propellor hub pocket. These cylinders make the part easier to print. Break them both out and clean up the pocket area before use.Follow the AMA Safety Code when using this part! Propellors and spinners that rotate at high speed are inherently dangerous. Use extreme care in fabricating and using this part. Use at your own risk!Three files are offered for this Thing. Files 2 and 3 are for makers having trouble building the two parts from a single file. Spinner 3--contains the spinner cap and the backing plate in a single file. Spinner Cap--contains just the cone of the spinner that snaps into the Plate