* Grade 3 Si3 N4 ceramic balls. Ceramic BB90 BB kit. ■ In the practical range is a rank among the finest, Grade 3. Silicon and noxious (Si3 N4) are a representative of non – oxide of ceramic, high strength, bending strength and stronger than the other ceramic under high temperature environment. Whats more, thermal expansion and dimension for better stability. ■ When you order, please check the bearing size (inside diameter, outside diameter) before you order. ■ 608 – 9 model number: outside diameter 22 mm inside diameter 9 mm thickness 7 mm * Product Color may vary depending on the type of display, actual product may vary slightly from the product image. This listing for the specification, improved the design of the logo, etc., may be altered. In addition, the manufacturers to reveal the answer your questions about the dimension and a personalized fit and you are not the actual product. Please understand and thank you.