Ответ:The "TUBE I.D." column is in reference to the rubber tube inside dimension to be used on that unit. These units have national pipe thread, which is a tapered thread, and not measured to identify the listed size, but if the hole has NPT threads, and is approx 1/2", then you most likely need a 1/4" NPT threaded unit. The AN840-6D is an aluminum fitting that has 1/4" NPT & would use a 3/8" I.D. rubber hose.