DK-LOK® fittings and valves are manufactured to the most rigorous and stringent indu4L can assist you with your sanitary and Bio-Pharm connections and components. We have many years of experience in both sanitary and Bio-Pharm industry. If certain finishes are required, we can provide all required documentation. 4L has partnered with Steel & O’Brien® to bring you the highest quality sanitary and Bio-Pharm components…available. stry standards. This has led DK-LOK® to be one of the most certified tube fitting and valve manufacturers in the world. 4L and DK-LOK®’s guarantee is a leak-tight seal in process, power, and instrumentation applications. 4L’s pledge is to provide our customers with reliable quality products and unprecedented quality customer service. As your fittings and valve provider, it is our responsibility to bring increased value to your company and facility/plant.