The 4 MM CS X 16.5 MM ID NBR (BUNA) 70 O-Ring by Freudenberg-NOK is a reliable sealing solution for various industrial applications. With a cross-section of 4 mm and an inner diameter of 16.5 mm, this O-ring is crafted from durable NBR (BUNA) material, ensuring a hardness rating of 70. It offers excellent resistance to a wide range of chemicals, making it suitable for hydraulic and pneumatic systems. This O-ring is designed to provide a secure seal, minimizing the risk of leaks and enhancing the performance of your machinery.