This is the most common size bearing in all reel applications from every manufacturer. Chances are, your reel has one of these in it! Most bait casting reels will use this size bearing either alone or in combination with another size. This includes most brands. Note: Hyper performance 3x10x4 sizing was the "Original" Spool Hi- Speed Bearing on which the company was founded. The initial prototypes were this size. The inner race chemical micro polishing which is now a process which we use on the 5x11x4 and 3x8x4 and 4x10x4 sizes was first introduced on the 4th prototype of this bearing. This size fits just about ALL Shimano.
* Most Daiwa Steeze takes this kit.
** Many Shimano reels require 8x12x3.5 for drive bearing.