The Yo-Yo bearing is a kind of bearing specially designed for Yo-Yo (also called Yo-Yo). The Yo-Yo bearings are divided into three types: ordinary type, special type and special type. 

 Most of the ordinary yo-yo bearings are deep groove ball bearings made of bearing steel. The bearings are miniature bearings and the inner diameters range from 3mm to 6mm. This type of bearing has a high speed, and most of them are open type and sealed type. 

 The special type yo-yo bearings are non-standard type of inch bearings, and the outer circle is U-shaped, also known as KK bearing. The best advantage of this type of bearing is that the U-shaped groove design conforms to the use characteristics of the yo-yo, which makes the yo-yo speed smooth. 

 The special enhanced version of the yo-yo bearing is also called high-precision KK bearing. As the name suggests, it is the KK bearing with high precision. The precision and material are the main factors affecting the bearing performance. It directly determines the price of the bearing, and the idling time is naturally longer than other bearings. The biggest advantage of this special bearing is that the rope will be in the center of the bearing as much as possible when playing the ball, reducing the friction between the rope and the ball wall. The common low-cost toy yo-yo in the market often uses sliding bearings instead of rolling bearings.

MR105ZZ,MR105-KK,

5mm x 10mm x 4mm - The A bearing fits most Duncan, Playmaxx, YoYoFactory, ZanNavi and many other yo-yos.

R168zz,R168-KK

.250 x .375 x .125 (1/4" x 3/8" x 1/8") - This bearing fits small bearing YoYoJam yo-yos, including SpinFaktors (but not the HG), Kamaitachi, Sunset Trajectory and Matrixx. It also fits the SuperYo Renegade, and the Spintastics Revolver and Eclipse.

R188ZZ , R188-KK

 .250 x .500 x .187 (1/4" x 1/2" x 3/16") - Fits the large bearing YoYoJam yo-yos including the Hitman, Lyn Fury, Spinmaster 2 and 3, Big Ben, Patriot, Nightmoves 2 and 3, Shockwave 3, the Speeder and the Speedmaker, as well as the YoYoFactory G5 and 888.

685ZZ,685-KK

 5mm x 11mm x 5mm - Fits B.I.S.T., HSpin and SPYY yo-yos.

R155ZZ,R155-KK

.156 x .312 x .125 (5/32" x 5/16" x 1/8") - Fits the Spintastics Tornado, Tigershark, Riot, Great White, Comet, Torch, and Firefly, and Yomega ball bearing yo-yos.