Bumper weights are solid high-density rubber. They are used primarily for cleans or snatches, where the bar is dropped to the floor from a significant height.
All brands of bumper plates listed below are the same 450mm (17.72") IWF regulation diameter, except as noted. This means that most brands can be mixed together on the same bar.
The Intek and Vulcan bumper plates have steel anchors in the hubs to prevent them from coming loose.