If you're looking for where the key to One Drop's success is, most of it has its own 10-Ball, flat stainless steel precision Ball Bearing.
If you thought that Vosun only made Yo-Yos of high performance at a low cost, you were very wrong... keep reading.
A Ceramic Concave stainless steel 8 BallBearing. These are replacement bearings with Concave profile and available in ILYY (metric) Size.
A Gold stainless steel 10 BallBearing size C.
A stainless steel 8 BallBearing Narrow Size C .
A Chrome Steel 8 BallBearing size C "Flat".