CP Series Poppet Check Valves, 1/4 in MNPT x 1/4 in MNPT, 316 SS, Cv: 0.35, Cracking Pressure: 1 psig

A 1 psig cracking pressure is about as low as you'll find on a poppet-style check valve, so it opens up real easy without needing much pressure behind it. Both ports are 1/4 in MNPT, so it'll thread right into a standard 1/4 in female NPT fitting on each end. The 316 stainless steel body holds up well where moisture or mild corrosives are a concern. Just keep in mind the Cv is 0.35, which means flow capacity is on the modest side, so it's best suited for lower-flow applications rather than high-volume lines.

Correct, the cracking pressure is one psig. This means it will start to open and allow flow when the pressure reaches one pound per square inch.