These DN 100 ISO-LF centering rings with fixed 30 mesh screen and Viton O-ring follow ISO-LF standards and have a flange size of ISO-100. These centering rings, with non-removeable 30 mesh screen, are useful in many situations in which a vacuum system or instrument needs to be protected from contamination by particulates generated from outside the system or from within. They are commonly used in between a turbo pump and foreline. These corrosion resistant stainless steel centering rings have an external Viton O-ring attached. VitonŽ is well known for its excellent resistance to heat (400°F/200°C) and to aggressive fuels and chemicals. VitonŽ is a registered trademark of DuPont Performance Elastomers.