It's called a barbell piece, and you need a barbell bar. Of course, there are also a few movements that can be exercised directly with barbell pieces. Barbell pieces have specifications, but the weight of barbell pieces will be different due to different manufacturers. Let's talk about the common weights here, mainly 25 kg, 20 kg, 15 kg, 10 kg, 5 kg, 2.5 kg or even 2 kg, 1.20.