When you choose Weight Plates, consider both your equipment and your goals. First, you have to know if the plate is going on a Standard bar or an Olympic bar. Then, consider how often you will be using the plates and how much weight you expect to lift. Standard barbells are 1 to 1 1/16 inches in diameter, and the hole in the center of plates for those bars should be about 1 5/32 inches. Olympic bars are from 1.949 to 1.969 inches in diameter, and the hole will be from 1.976 to a maximum of 2 inches. If the plates vary from these dimensions, they probably will not fit at all or may slide around on the bar.
Besides the traditional plates, many manufacturers make Grip Plates, with cutouts in the metal to make it easier to grasp the plates, but this is a matter of personal preference. Use the same type for all your plates, or for the ones you will use on a given bar. It is worth the investment to buy more expensive plates because they fit the bar better and are more consistent in size. Good weight plates can last 50 years. Bumper Plates are made of rubber. They are used in Olympic-style weightlifting, including the clean and jerk and the snatch. Because of the rubber, they do not bang and damage the floor as easily.