These adapters are male 1/4 NPT to 1/4 inch air valve stem feedthrough. They are commonly used for temporarily adding positive air pressure to test vacuum lines. The 1/4 inch air valve stem is standard and connects to most air compressor hose fittings and lines.

WARNING: Brass alloys contain Zinc. Zinc will outgas from brass under certain combinations of elevated temperature and high-vacuum. System damage may occur if these conditions are present.