Koolance patented quick disconnect no-spill coupling with automatic shutoff. G 3/8 BSPP (parallel) thread female fitting for screwing directly into a water block or other component of same threading. It will only fit a Koolance QD4 male quick disconnect.After pulling the ring on the female QDC side, the quick-disconnect fittings will separate. Liquid on both sides will be automatically obstructed with approximately 0.2ml freed. Coolant volume lost upon disconnection will rise with internal pressure higher than 0.5kgf/cm2 (7psi).