Hoke and Circle Seal check valves are engineered with no compromise of quality and performance to meet the growing requirements of non-return valves in instrumentation systems. Poppet and Ball verions. Very low opening pressures for precise control and low pressure systems. Available in Stainless Steel 316 and exotic materials loke Monel, Hastelloy, Inconel, Incoloy, Duplex, Super Dulex etc. All NPT threads are High Tolerance.