Want some extra spin time and performance? Dif-E-Yo KonKave bearings are a great way to upgrade any yo-yo. KonKave bearings keep the yo-yo's string centered at all times during play reducing friction against the yo-yo's body. Available in two sizes Size A and Size C (small & large) and made from stainless steel. These bearings a must for any pro player! US Patent #7175500