1/4" Pipe to 1/8" Male Thread Non-return Elbow - Quick Fit Type
This fitting is typically used on the "product water" outlet of a domestic RO's membrane (1812) housing, where the water flows to the storage tank and tap. The non-return elbow has a stainless steel spring lever inside of it, which will allow water to flow through one direction (from the thread side to the 1/4" pipe side), but it will prevent water from flowing back in the other direction (so from the 1/4" pipe side to the thread side of the fitting).