Includes (2) 25kg, (2) 20kg, (2) 15kg, (2) 10kg bumper plates.
Standard colors, 450mm diameter, and a steel hub with a precisely machined hole that fits snugly on the bar.
You will need competition bumpers if you're lifting over 180 kg or so. The color coding also helps prevent mishaps with mismatched weight. The large steel hub is heavier than rubber, so the plate ends up being thinner than a solid rubber bumper. Less rubber also means the bounce will be lower and more controlled.
On the downside, comp bumpers are not good for high-rep workouts with low weight (the green 10kg bumper by itself). They are thin and can get damaged easier, even though they are high quality. So if you're unsure, get economy bumpers.