6217 bearing, deep groove ball bearings are one of the most common styles of ball bearings which support axial forces in both directions as well as radial forces. The bearing has a single row of balls retained in a cage. This style of bearing you are viewing is what we call open style (no seals or shields), allowing the lubricant to flow around the bearing freely. Open bearings tend to be used in applications like gearboxes.

Some bearings exist with more or less important variants (large or small internal clearance, special grease, very high temperature, etc ...). These variants are always indicated by prefixes and suffixes in the reference.