1---Different sizes: four different sizes: suitable for weight discs with diameters of 25 mm, 28 mm and 30 mm. You can refer to the image and details page to measure and select the size. If you are not sure of the appropriate size of the barbell clip, you can ask the seller. 2---High quality materials: stop disc must also be environmentally friendly. We only make products that consumers are happy with: high quality spring steel, hard and firm, plastic handles, clean and environmentally friendly, safe and secure, easy and quick to assemble and disassemble, making it easy to get back into shape. 3---Exercise safely: our dumbbell collar can take a lot of weight and exercise, making it great for weightlifting and strength training. It's ideal for use with dumbbells, squat machines and other sports equipment. It's essential equipment for athletes, fitness rats and bodybuilders. 4---Easy to use:The firm grip and comfortable, soft plastic handle make the spring clamp easy to install and remove. Simply attach the clamp to the training equipment and release. 5---Wide range of applications: spring clamp is suitable for both smooth and spiral rods. It can help you adjust the weight of your dumbbells more quickly and safely in the gym, weight training and bodybuilding. Material: plastic + stainless steel 2.5cm model: inner diameter 2.5cm, length 8cm, suitable for rods between 2.5-2.6cm. 2.8cm model: inner diameter 2.8cm, length 8.5cm, suitable for rods between 2.8-2.9cm. 3.0cm model: inner diameter 3cm, length 8.5cm, applicable to rods between 2.9-3.0cm.