The difference between the two is the 5 is the previous data link tool now the 6 is the latest and fastest interface tool meaning that it converts the data faster from the ecm to the laptop.
The inline 5,6 is the tool you use to hook up to the truck and to your computer that basically talks to the ecm and converts the data from the ecm to your computer to be able to be viewed on the computer. There are several different versions of insite from the free version all the way up to the pro version and they all cost different prices and they are bought with a yearly subscription. Well insite is the Cummins electronic service diagnostic tool. P art 1: Cummins Inline 5 and Inline 6 Comparison :
