the D6 and D6 XE (the XE is the outlier in this new future of no letter modifiers because Cat needed some way to denote a premium model) replaced the D6; and the D7 replaced the D7E and D7R.
suite of features will be included as a standard feature on Cat D4, D5, D6, D6 XE and D7 models. Additionally, a new Cat Grade with 3D Ready option provides flexibility for customers upgrading to ...