The balls in these bearings are high precision grade 10 balls which are 10/1000000” from exactly round. The races these bearings run in are made from a high carbon chromium alloy steel. The cage the balls sit in are made from riveted steel to yield superior strength. They have two rubber LLB seals that are best suited to hubs. Many bearings on the market do use the “2RS” term but do use caution because lots of these bearings only have a seal making contact with the inner race. This allows contamination to quickly penetrate the bearings and render them useless. 2RS to us is a proper rubber seal on both the inner and outer race giving superior sealing.
All bearings come in pairs