Size A or ' 5x10x4mm' is a very unusual size in today's professional Yo-Yos. But if you need one, find it here. Small bearings Size A always offer higher spin speed than standard models.
The Dif-e-Yo KonKave Stainless Bearing centers the string while at the same time allowing it to move when needed for response. Size A (5x10x4 mm). For all Duncan Yo-Yos, YoYoFactory...