The unique ring disc design ensures that the disc remains light and responsive even in large sizes, which is essential for rapid non-slam closure. Mounted on a multiple spring and radial guide assembly, the disc moves freely without the frictional forces. Combining two ring-shaped annular flow paths with the excellent pressure recovery properties provided by the diffuser, the minimal pressure drop across the Type N valves gives lifetime energy savings when compared to more conventional check valve designs. It is also available with the API 6D face-to-face dimensions (Series ND)