O-Rings are specifically used to create what type of barrier?

O-rings are specifically designed to create an airtight seal between two surfaces, preventing the passage of fluids or gases. They are circular in shape and made from materials that can effectively compress and deform to fill any gaps, ensuring a secure barrier. This makes them ideal for applications where maintaining a tight seal is crucial, such as in hydraulic systems, engines, and various machinery where pressure and fluid containment are essential.

The other options describe barriers that O-rings do not specifically address. Structural barriers pertain to load-bearing supports, electrical barriers involve insulating materials used to prevent electrical conduction, and weight-bearing aspects focus on structures intended to support a load, none of which are functions of O-rings. Thus, their primary role is in creating airtight seals, making them essential in ensuring the integrity and performance of many engineering applications.