BULKHEAD UNION/NYLON/ Tube to Tube, 1/2 inch tube outside diameter. 282N08NYLO-Seal Bulkhead Union | Fits 1/2in TubingNYLO-Seal Nylon Bulkhead Unions have excellent resistance to acids, alkalis, dilute mineral acids, most organic acids, petroleum oils and greases, and photographic solutions. Install..