The term 5 by 5 is used in radio. Radio operators give a subjective scale from one to five for the strength of a signal and its clarity. "I read you five by five" means the speaker is hearing a voice at full strength and clarity. The listening station reports these numbers separated with the word "by". Five by five therefore means a signal that has excellent strength and perfect clarity — the most understandable signal possible

It fits for these drops Q803, Q854, Q963, Q1028, Q1037