Bumper weights are solid rubber, named for the way they are meant to be bumped around.
They are used primarily for exercises such as cleans or snatches, where the bar is dropped to the floor from overhead, or otherwise set down hard in a controlled motion, and requires the weight plates to sustain such an impact.
Bumper plates are all the same diameter, regardless of weight. Regulation size is 450mm (17.71") diameter, but different brands can vary anywhere from 17.5" to 18". You want them all to be the same size, so it's best to get a set of all the same ones and avoid hoping to get more of the same model later.
The hole is usually covered with a solid steel insert or sometimes brass. Cheaper bumper plates in the past have sometimes been made with a large part of steel or iron, and rubber coated the last few inches, to save money and give the appearance of being solid rubber. However, manufacturers and consumers have wised up to the fact that all-rubber is more durable, and all of the bumper plates we offer here are all-rubber.
Bumpers are often used with a lifting platform, consisting of a hardwood surface where you stand and rubber mats covering the surface to your sides where the weights touch the floor. The combination of bumper plates and rubber mats ensures maximum impact absorption. For home users setting up a garage gym, including Crossfitters, the most cost-effective method is to skip the wooden lifting platform and lay down rubber mats, either one mat on each side or spread over the entire area.
We don't recommend using a cheap olympic bar if you're going to be dropping the loaded bar with bumpers. They can bend under that kind of force. If you're going to spend the money on bumpers, get a higher quality bar too.
Don't forget to get a storage rack to neatly store your bumper weights. It's annoying and unsafe to leave the equipment on the floor. You can get any olympic or standard storage rack. Standard posts will cause bumper plates to dangle loosely, but some people actually prefer that because they can slip them on and off so easily. Horizontal bumper weight racks that lay on the floor and have slots for each plate are good for placing near each of a lifting platform, and it's what professional environments use.