High quality stainless steel ball bearings from Japanese manufacturers (NMB, NSK), comparable to those on Shimano and Daiwa reels. These have the more durable races than Anti-rust bearings. So, for reels to be used in freshwater, these should be used for longer life. These ball bearings conform to JIS-0, Japan Industrial Standard Class 0, suitable for high speed spin in fishing reels.
"Open" bearings do not have side shields.
"Anti-rust" bearings have more salt resistance.
"Flanged" bearings have flanges.

inner dia x outer dia x thickness (mm)