Is there something as “u” type bearing?i saw it on ebay while searching for a yoyo.
I believe U type bearings are the same as concave bearings. They’re called “U type” presumably cause the shape of the concavity forms a U-like shape.
there is also V shaped and _/ or Centre Track
The Buddha Whipple bearing is more of a / v-type shape.
U-shape is a generic term for any concave bearing. This term normally excludes any of the grooved bearings and CenterTracs. The U-shape can be more or less dramatic on some versions. Be aware of quality issues, especially with the low prices.
U and V groove type bearings are known as “track bearings” in the non yoyo world.
They were made to run on rails for liner motion products.
Most bearing manufacturers have made them in many sizes and shapes for many years.
Search it and see…