Optimize realizes that your time is valuable and should not be wasted worrying about fittings. For this reason, all Opti-Lock Fittings are precision machined in the USA for optimal quality and thread consistency. The machining process is the best way to ensure tight manufacturing tolerances and minimal product variance. What does all this mean? It means that every fitting you purchase from Optimize will perform just as well as the last, so you'll have no worries about faulty fittings. This reflects our commitment to providing our customers with the highest quality, best designed product available.