With over 40 years of experience designing, engineering, and manufacturing Instrumentation Valves and Fittings , Hy-Lok continues to set the world standard for quality and performance. Hy-Lok manufactures Instrumentation Tube, Flare & Pipe Fittings in sizes 1/16 inch through 2 inch, Ball Valves, Double Block and Bleed, Needle & Check Valves.