D bearings? Why?

[Malachi]

From a conversation about bearing blanks.

Bearing Blanks

Just wanted to thank @YoYoExpertGarrett for the Bearing Blanks. I notice @Mystik got a few as well in the mail. For all of you that were getting a few Bearing Blanks to try out, this can be the thread to keep track of our thoughts and share our experiences all in one place. Just searching the forums, Bearing Blanks have been an ongoing topic within threads but does’t have a home. Here are the ones I just received from @YoYoExpertGarrett; 1/2 Spec C Maple 1/2 Spec C Acrylic D size Maple Blank 2…

Width can be a little more complicated.

A bearing is MR105: 5 x 10 x 4mm
C bearing is R188: .250 x .500 x .187 inches or 6.35 x 12.7 x 4.7498mm
D bearing is 658: 5mm x 11mm x 5mm

but…
A bearings have a 3mm wide version.
C bearings have a half-spec version (that is wider than half), 0.125 in wide or 3.175mm.
D has a 4mm wide variant, MR115, and a 3mm wide variant, 685.