A:AnsweriPad Pro generation 1 (2015) and generation 2 (2017) had a larger border around the screen making it overall bigger but the viewable area on all 12.9" sizes are the same just that the generation 3 (2018) has a smaller outside border so it has to have a different size case.
A:AnswerThe newest iPad Pro 12.9" is an amazing technological accomplishment in that Apple managed to make their biggest and best iPad Pro 12.9" housing smaller than ever, yet keep the 12.9" screen size. That means the purchasers of the newly released iPad 12.9" iPad Pro ( November 2018) require a different size case than previous 12.9" iPads. When folks reply that the case fits 1 or 2nd generation it confuses purchasers of the iPad Pro 12.9" November 2018 model.
