These KF-25 Metal Hose Bellows Vacuum Works Well,High temperature resistance, negative pressure resistance, corrosion resistance and wear resistance. Easy to install, easy to disassemble, safe to use,Stainless steel material, Soft, flexible, easy to bend, vibration absorbing,It has already passed the helium leakage test,Interface size standards, These KF-25 Metal Hose Bellows Flex Coupling vacuum fittings follow ISO-KF standards and have a flange size of NW-25.