Copper O-Ring 
1.widely used in machine design 
2.Can with FG NA filled. 

Copper O-Ring  are designed to be a seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. It is one of the most common seals used in machine design. They are inexpensive and easy to make, reliable, and have simple mounting requirements. They can seal thousands of psi pressure.