Bicycle bearings all abouts, most of the Bicycle bearings have rubber seals to protect the bicycle bearings from dirt, dust or any possible contamination, Bicycle bearings are lubricated with grease, you can always remove the seals, relubricate the sealed Bearings with grease then put the seals back again. Bicycle bearings has item number ends with 2RS which stands for 2 rubber seal enclosures.