ORIGINAL: Cross
Click on the big red "here" in the auction and it takes you to a site that describes all the bearings available. You can get metal shield, rubber shield, colored shields, steal balls, ceramic balls, even stainless balls. This allows you to pick and choose the best bearing for its specific application vs, just buying the assortment the seller has made up.
Well I guess for picking which BB set will be the rubber shield if running in wet conditions obviously.