These are PC series pneumatic quick-connect fittings made of brass with blue plastic push-in releases.They are designed for industrial applications requiring rapid, reliable connections in air compression or vacuum systems.Common sizes available include tube diameters from 4mm to 16mm and thread sizes such as 1/8", 1/4", and 1/2".Fittings like these typically feature a maximum operating pressure of around 145 psi (10 bar) and operating temperatures between 0°C and 60°C