The Erde Hub-cover Prevents dirt and dust from getting to the wheel bearings and causing wear.
It should only be removed when tightening the wheel or replacing the bearings.
Removal of the hub cap is a matter of systematically tapping around it, in an outward motion with a nylon or hide mallet until it pops out, ensure that it is perfectly clean if the intention is to re-use it.
A new hub-cover is fitted by lightly tapping it into place after first packing the hub with grease.