The O-ring is made of rubber, and it is safe and non-toxic. The sealing ring is suitable for boat, car, machine tool aeronautical facility and so on. It can be used repeatedly and durable for long time use. Features: Made of rubber, safe and non-toxic, odorless and durable. The sealing ring is suitable for boat, car, machine tool, aeronautical facility and so on. The sealing ring is abrasion-resistant, oil-proof, and dustproof. Easy to use: portable and can be brought along anywhere you go. Reusable and durable: the sealing ring can be used repeatedly and durable for long time use. Specifications: Condition: 100% New Material: Rubber Case Color: Blue, Yellow(Optional) Size: approx. 23.5*17*4.3cm/ 9.25* 6.69* 1.69in Weight: approx. 541g/ 19.08oz Package List: A Set of 363pcs O-rings(for blue style) A Set of 366pcs O-rings(for yellow style) Note: 1. Please allow 0-2cm error due to the manual measurement. Thanks for your understanding. 2. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.