What Is an O-Ring?
An O-ring is a doughnut-shaped (toroidal) elastomer seal with a circular cross-section. When compressed in a groove between two surfaces, it deforms to fill the gap and prevent fluid passage. O-rings are the simplest and most widely used seal type in hydraulic, pneumatic, and static applications.
Material Selection
NBR for hydraulic oils. FKM for high-temp and aggressive fluids. EPDM for water and steam. Silicone for food-grade and medical. FFKM for extreme chemical resistance. Available from SMS Bearings through our Sealing Solutions range.
Frequently Asked Questions
How do I select the right O-ring size?
O-rings are specified by inner diameter (ID) and cross-section diameter (CS). Standard sizing follows AS568 (imperial) or ISO 3601 (metric) series. The groove must compress the O-ring by 10-30% of its cross-section to achieve a proper seal. Always specify the material based on the fluid and temperature.