What type of bearings to use in a wheel on grinder

[Railrider1920]

Hey folks,
What type of bearings are good to use on wheels for grinders? At my local fastenal I can get roller bearings, ball bearings, sleeve bearings and radial ball bearings.
http://www.fastenal.com/web/search/...|~ ~|categoryl2:"610631 Unmounted Bearings"|~

I was reading some of the "caster" threads to see what was used, but the only type I saw mentioned were needle bearings, and they were being replaced. So what type of bearings be used in a wheel that will spin that fast?

Thanks

 

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http://www.fastenal.com/web/products/detail.ex?sku=0474494

 

[Railrider1920]

Thank you kind sir