Fittings DK-Lok brings you excellent quality Outstanding customer service. and availability Enjoy Dk-Lok tube fitting working your application ! DO Series O-Ring Face Seal Fittings Catalog 2D / 3D Spec. Size : 1/8″ to 1″ (DO Size) Material : Stainless Steel 316/316L Tube, NPT, SAE thread, and weld connections Brief Description Designed for rapid assembly in pipe, tube, and welded system. Unique design allows easy installation where spce is limited. No axial clearance is required. Sealing is accomplished with a captive O-ring in the body component. Assemblieds can be used from high pressure to critical vacuum, within a wide range of temperature.