Is your center bearing a 608 or an R188? We Don’t Care! These caps will fit in Either Size!! Ok, that’s not exactly true, but you do get both sizes in one order. That way, even if you aren’t sure what size bearing your spinner is using, you are ready to rock right out of the package. We have beefed these up to be extra thick because it looks cool, and it will allow most spinners to table spin. Just in case your into that kind of thing. The super fine detail in the machining just looks sexy on any spinner you want to put these on.