UNC is Ultralight Non-Coated,which means the rims are original natural carbon surface ,without any coatings/painting . First of all,regular rims from the mold,need a lot of processing links:grinding,drilling,painting,labeling,to the final shipment.Of course,during this process,each rim needs to go through with a number of links of quality testing including the flatness testing,roundness testing,weight testing,as well as tire pressure testing and so on.