These WPC-treated bearings are the best we have seen!?WPC is a shot-peening treatment at a microscopic level. It's perfect for sensitive surfaces like bearings. The WPC treatment removes imperfections and high spots, while creating a surface that retains oil better than the original surface. This greatly reduces friction. The bearings in this kit are original equipment Glyco bearings that are sent to WPC for treatment. The treated bearings are stronger with less metal fatigue and less friction than buying off-the-shelf bearings from the dealer.