Inert flow path, with no springs, no metal. Flow path equivalent to 0.030" orifice. PEEK housing, with three choice of check valve element, EPDM, Viton, or Chemraz. Small internal volume, 49-68 µl, depending upon version Low crack pressure 1 to 0.3 psi depending upon element. Check against backflow to 100 psig. 1/4-28 threads.